NASA Television is available in continental North An overview of the mission will be presented in a
America, Alaska and Hawaii by C-band signal via news conference broadcast on NASA TV and on
Satellite AMC-18C, at 105 degrees west longitude, http://www.ustream.tv/nasajpl, originating from NASA
transponder 3C, 3760 MHz, vertical polarization. A Headquarters in Washington, at 1 p.m. EDT on
Digital Video Broadcast-compliant Integrated Receiver July 16, 2012. Back-to-back briefings on Aug. 2, 2012,
Decoder is needed for reception. Transmission format at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.,
is DVB-S, 4:2:0. Data rate is 38.80 Mbps; symbol rate will present information about the mission’s science
28.0681, modulation QPSK/DVB-S, FEC 3/4. goals and capabilities at 10 a.m. PDT, and about
the flight and planned landing at 11 a.m. Pre-landing
NASA-TV Multichannel Broadcast includes: Public update briefings at JPL are scheduled for 9:30 a.m.
Channel (Channel 101) in high definition; Education PDT on Aug. 4 and 9:30 a.m. on Aug. 5. A post-launch
Channel (Channel 102) in standard definition; and Media briefing at JPL will begin within about an hour of the
Channel (Channel 103) in high definition. anticipated landing time (10:31 p.m. PDT) under most
conditions, and within about three hours of the landing
For digital downlink information for each NASA TV chan- time if the spacecraft’s status is unknown. All of these
nel, access to all three channels online, and a schedule briefings will be carried on NASA TV and on http://
of programming for Mars Science Laboratory activities, www.ustream.tv/nasajpl. Specific information about
visit http://www.nasa.gov/ntv. upcoming briefings, as they are scheduled, will be kept
current on the Internet at http://www.nasa.gov/msl.
Media Credentialing
Live Feed
News media representatives who would like to cover
the launch in person must be accredited through the A live feed of video during key landing activities from
NASA Jet Propulsion Laboratory’s Media Relations the mission control room at JPL will be carried on
Office. To apply for credentials, visit http://media- NASA TV and on http://www.ustream.tv/nasajpl be-
credentials.jpl.nasa.gov. Specific questions about the tween about 9 and 11 p.m. PDT on Aug. 5 (midnight
credentialing process may be submitted to media- and 2 a.m. EDT on Aug. 6).
credentials@list.jpl.nasa.gov. Journalists may con-
tact the JPL newsroom at 818-354-5011 for more Internet Information
information.
Information about NASA’s Mars Science Laboratory
mission, including an electronic copy of this press kit,
press releases, status reports and images, is available
at http://www.nasa.gov/mars and http://marsprogram.
jpl.nasa.gov/msl. Frequent updates about the mission,
together with public feedback, are available by follow-
ing Curiosity on Twitter at http://www.twitter.com/
marscuriosity and on Facebook at http://www.
facebook.com/marscuriosity.

• One of five planets known to ancients; Mars was • Atmosphere composed chiefly of carbon dioxide
the Roman god of war, agriculture and the state (95.3 percent), nitrogen (2.7 percent) and argon
• Yellowish brown to reddish color; occasionally the (1.6 percent)
third-brightest object in the night sky after the moon • Surface atmospheric pressure less than 1/100th
and Venus that of Earth’s average
• Surface winds of 0 to about 20 miles per hour (0 to
Physical Characteristics about 9 meters per second), with gusts of about
90 miles per hour (about 40 meters per second)
• Average diameter 4,212 miles (6,780 kilometers); • Local, regional and global dust storms; also whirl-
about half the size of Earth, but twice the size of winds called dust devils
Earth’s moon
• Surface temperature averages minus 64 F (minus
• Same land area as Earth, reminiscent of a cold, 53 C); varies from minus 199 F (minus 128 C)
rocky desert during polar night to 80 F (27 C) at equator during
• Mass 1/10th of Earth’s; gravity only 38 percent as midday at closest point in orbit to sun
strong as Earth’s
• Density 3.9 times greater than water (compared with Features
Earth’s 5.5 times greater than water)
• No planet-wide magnetic field detected; only local- • Highest point is Olympus Mons, a huge shield vol-
ized ancient remnant fields in various regions cano about 16 miles (26 kilometers) high and 370
miles (600 kilometers) across; has about the same
area as Arizona
Orbit
• Canyon system of Valles Marineris is largest and
• Fourth planet from the sun, the next beyond Earth deepest known in solar system; extends more than
2,500 miles (4,000 kilometers) and has 3 to 6 miles
• About 1.5 times farther from the sun than Earth is (5 to 10 kilometers) relief from floors to tops of sur-
• Orbit elliptical; distance from sun varies from a mini- rounding plateaus
mum of 128.4 million miles (206.7 million kilometers)
to a maximum of 154.8 million miles (249.2 million Moons
kilometers); average is 141.5 million miles (227.7
million kilometers) • Two irregularly shaped moons, each only a few
• Revolves around sun once every 687 Earth days kilometers wide
• Rotation period (length of day): 24 hours, 39 min- • Larger moon named Phobos (“fear”); smaller is
utes, 35 seconds (1.027 Earth days) Deimos (“terror”), named for attributes personified
• Poles tilted 25 degrees, creating seasons similar to in Greek mythology as sons of the god of war
Earth’s

Mars Science Laboratory Landing 7 Press Kit
Mars Science Laboratory Investigations
Mars Science Laboratory Investigations croorganisms or their fossil equivalents. However, if this
mission finds that the field site in Gale Crater has had
NASA’s Mars Science Laboratory mission will study conditions favorable for habitability and for preserving
whether the Gale Crater area of Mars has evidence of evidence about life, those findings can shape future
past and present habitable environments. These studies missions that would bring samples back to Earth for
will be part of a broader examination of past and present life-detection tests or for missions that carry advanced
processes in the Martian atmosphere and on its surface. life-detection experiments to Mars. In this sense, the
The research will use 10 instrument-based science Mars Science Laboratory is the prospecting stage in a
investigations. The mission’s rover, Curiosity, carries the step-by-step program of exploration, reconnaissance,
instruments for these investigations and will support their prospecting and mining evidence for a definitive an-
use by providing overland mobility, sample-acquisition swer about whether life has existed on Mars. NASA’s
capabilities, power and communications. The primary Astrobiology Program has aided in development of the
mission will last one Mars year (98 weeks). Mars Science Laboratory science payload and in stud-
ies of extreme habitats on Earth that can help in under-
The payload includes mast-mounted instruments to standing possible habitats on Mars.
survey the surroundings and assess potential sampling
targets from a distance; instruments on Curiosity’s Three conditions considered crucial for habitability are
robotic arm for close-up inspections; laboratory instru- liquid water, other chemical ingredients utilized by life
ments inside the rover for analysis of samples from and a source of energy. The Mars Science Laboratory
rocks, soils and atmosphere; and instruments to moni- mission advances the “follow the water” strategy of
tor the environment around the rover. In addition to the NASA Mars exploration since the mid-1990s to a
science payload, engineering sensors on the heat shield strategy of determining the best settings for seeking an
will gather information about Mars’ atmosphere and the answer to whether Mars ever supported life.
spacecraft’s performance during its descent through the
atmosphere. Every environment on Earth where there is liquid water
sustains microbial life. For most of Earth’s history, the
To make best use of the rover’s science capabilities, a only life forms on this planet were microorganisms, or
diverse international team of scientists and engineers will microbes. Microbes still make up most of the living mat-
make daily decisions about the rover’s activities for the ter on Earth. Scientists who specialize in the search for
following day. Even if all the rover’s technology performs life on other worlds expect that any life on Mars, if it has
flawlessly, some types of evidence the mission will seek existed at all, has been microbial.
about past environments may not have persisted in the
rock record. While the possibility that life might have Curiosity will land in a region where this key item on the
existed on Mars provokes great interest, a finding that checklist of life’s requirements has already been deter-
conditions did not favor life would also pay off with valu- mined: It was wet. Observations from Mars orbit during
able insight about differences and similarities between five years of assessing candidate landing sites have
early Mars and early Earth. made these areas some of the most intensely studied
places on Mars. Researchers have used NASA’s Mars
Habitability Reconnaissance Orbiter to map the area’s mineralogy,
finding exposures of clay minerals. Clays, other phyllosili-
The mission will assess whether the area Curiosity ex- cates and sulfates form under conditions with adequate
plores has ever been a potential habitat for Martian life. liquid water in a life-supporting, medium range between
very acidic and very alkaline.
Whether life has existed on Mars is an open question
that this mission, by itself, is not designed to answer. Curiosity will inventory other basic ingredients for life,
Curiosity does not carry experiments to detect active seek additional evidence about water and investigate
processes that would signify present-day biological how conditions in the area have changed over time.
metabolism, nor does it have the ability to image mi- The wet environment in which the clay minerals formed

Mars Science Laboratory Landing 8 Press Kit
is long gone, probably occurring more than 3 billion process would favor increased concentration of heavier
years ago. Examining the geological context for those isotopes in the retained, modern atmosphere. Such
minerals, such as the minerals in younger rock layers, processes can be relevant to habitability and biology.
could advance understanding of habitat change to drier Curiosity will assess isotopic ratios in methane if that
conditions. The rover can also check for traces of water gas is in the air around the rover. Methane is an organic
still bound into the mineral structure of rocks at and near molecule, and its carbon isotope ratio can be very
the surface. distinctive. Observations from orbit and from Earth indi-
cate traces of it may be present in Mars’ atmosphere.
Carbon-containing compounds called organic mol- Isotopic ratios could hold clues about whether methane
ecules are an important class of ingredients for life that is being produced by microbes or by a non-biological
Curiosity can detect and inventory. This capability adds process.
a trailblazing “follow the carbon” aspect to the Mars
Science Laboratory, as part of the sequel to the “follow The mission has four primary science objectives to
the water” theme. meet NASA’s overall habitability assessment goal:
• Assess the biological potential of at least one target
Organic molecules contain one or more carbon atoms environment by determining the nature and inven-
bound to hydrogen and, in many cases, additional ele- tory of organic carbon compounds, searching for
ments. They can exist without life, but life as we know the chemical building blocks of life and identifying
it cannot exist without them, so their presence would features that may record the actions of biologically
be an important plus for habitability. If Curiosity detects relevant processes.
complex organics that are important to life on Earth, • Characterize the geology of the rover’s field site at
such as amino acids, these might be of biological origin, all appropriate spatial scales by investigating the
but also could come from non-biological sources, such chemical, isotopic and mineralogical composition of
as carbonaceous meteorites delivered to the surface of surface and near-surface materials and interpreting
the planet. the processes that have formed rocks and soils.

Curiosity will also check for other chemical elements • Investigate planetary processes of relevance to past
important for life, such as nitrogen, phosphorus, sulfur habitability (including the role of water) by assessing
and oxygen. the long-time-scale atmospheric evolution and de-
termining the present state, distribution and cycling
The rover will definitively identify minerals, which provide of water and carbon dioxide.
a lasting record of the temperatures, pressures and • Characterize the broad spectrum of surface ra-
chemistry present when the minerals were formed or diation, including galactic cosmic radiation, solar
altered. Researchers will add that information to obser- proton events and secondary neutrons.
vations about geological context, such as the patterns
and processes of sedimentary rock accumulation, to Preservation and Past Environments
chart a chronology of how the area’s environments have
changed over time. Energy for life on Mars could come Some of the same environmental conditions favorable
from sunlight, heat or mixtures of chemicals (food) with for life can, paradoxically, be unfavorable for preserv-
an energy gradient that could be exploited by biological ing evidence about life. Water, oxidants and heat, all of
metabolism. The information Curiosity collects about which can contribute to habitability, can destroy organic
minerals and about the area’s modern environment will molecules and other possible markers left by life, or
be analyzed for clues about possible past and present biosignatures.
energy sources for life.
Life has thrived on Earth for more than 3 billion years,
Curiosity will measure the ratios of different isotopes of but only a miniscule fraction of Earth’s past life has
several elements. Isotopes are variants of the same ele- left evidence of itself in the rock record on this planet.
ment with different atomic weights. Ratios such as the Preserving evidence of life from the distant past has
proportion of carbon-13 to carbon-12 can provide in- required specific, unusual conditions. On Earth, these
sight into planetary processes. For example, Mars once windows of preservation have included situations such
had a much denser atmosphere than it does today, and as insects encased in amber and mastodons im-
if the loss occurred at the top of the atmosphere, that

Mars Science Laboratory Landing 9 Press Kit
mersed in tar pits. Mars won’t have fossils of insects or ing conditions over a range of times. Analyzing samples
mastodons; if Mars has had any life forms at all, they from different points in that range could identify which, if
were likely microbes. Understanding what types of any, hold organics. The rover might find that the answer
environments may have preserved evidence of microbial is none. While such an answer could shrink prospects
life from billions of years ago, even on Earth, is still an for finding evidence of ancient life on Mars, it would
emerging field of study. strengthen the contrast between early Mars and early
Earth. The history of environmental changes on an
To determine whether Mars ever supported life, a key Earth-like planet without life would be valuable for un-
step is learning where biosignatures could persist. derstanding the history of life’s interaction with Earth’s
Curiosity’s findings about windows of preservation will environment.
serve this mission’s prospector role: identifying good
hunting grounds for possible future investigations about Modern Environment
Martian life’s existence and characteristics. They can
also guide this mission’s own course, informing deci- The Mars Science Laboratory will study the current envi-
sions about where to drive and which rocks to sample ronment in its landing region as well as the records left by
in Curiosity’s search for organics. past environments. Curiosity carries a weather station, an
instrument for monitoring natural high-energy radiation
Accumulation of rock-forming sediments writes a record and an instrument that can detect soil moisture and wa-
of environmental conditions and processes into those ter-containing minerals in the ground beneath the rover.
sedimentary rocks. The layers of the mountain inside The investigations of organics and other potential ingre-
Gale Crater provide a record of events arranged in dients for life can analyze samples of modern-day soil for
the order in which they occurred. Researchers using what nutrients would be available to soil microbes. The
Curiosity can look at how environments changed over ability to check for methane in the atmosphere is a study
time, possibly including transitions from habitable condi- of modern processes, too. Methane would break down
tions to non-habitable conditions. Some of the clues are and disappear from the atmosphere within a few centu-
in the textures of the rocks, and Curiosity will be look- ries if not replenished by an active source, so its pres-
ing for distinctive rock textures. Other clues are in the ence would be surprising.
mineral and chemical compositions.
Selection of Curiosity’s landing site was not based on
Some conditions and processes, such as low tempera- traits favoring present-day habitability. However, much of
tures and rapid entrapment in the sediments, can favor the information this mission contributes about the mod-
preservation of organics and evidence about life. As ern environment will enhance our general understanding
Curiosity looks for organics by analyzing samples drilled of Mars. For example, can organic compounds delivered
from sedimentary rocks, it will be reading the history of by meteorites persist in the soil close to the surface?
past environments whether or not it finds organics. How does the modern atmosphere affect the ultraviolet
and high-energy radiation that reaches the surface, pos-
Some minerals and other geologic materials, such as ing a hazard to life and to preservation of organics? How
sulfates, phosphates, carbonates and silica, can help might we better estimate levels in the past? The rover’s
preserve biosignatures. All of these materials, forming monitoring of radiation levels from cosmic rays and the
under just the right balance of environmental conditions, sun also is designed to address astronaut safety on
have the potential to preserve fragments of organic mol- eventual human missions to Mars.
ecules derived from microbes or carbonaceous mete-
orites. But not just any rock formed of suitable minerals Science Payload
will do. Most on Earth do not. Expectations for Mars are
similar, and the chances of a discovery — even if life had On April 14, 2004, NASA announced an opportunity
been present — are very small. If this sounds sobering, for researchers to propose science investigations for
it should be, but this is the only known way to prospect the Mars Science Laboratory mission. The solicitation
for the vestiges of life on the early Earth. for proposals said, “The overall science objective of the
MSL mission is to explore and quantitatively assess a
The area at Gale Crater accessible to Curiosity as it potential habitat on Mars.” Eight months later, the agency
drives during the mission contains rocks and soils announced selection of eight investigations proposed
that may have been originally deposited under differ- competitively. In addition, Spain and Russia would each

Mars Science Laboratory Landing 10 Press Kit
provide an investigation through international agree- complementary capabilities for showing the rover’s sur-
ments. The instruments for these 10 investigations make roundings in exquisite detail and in motion.
up the science payload on Curiosity.
The right-eye Mastcam looks through a telephoto lens,
The two instruments on the mast are a versatile, revealing details near or far with about three-fold better
high-definition imaging system, and a laser-equipped, resolution than any previous landscape-viewing camera
spectrum-reading camera that can hit a rock with a on the surface of Mars. The left-eye Mastcam provides
laser and observe the resulting spark for information broader context through a medium-angle lens. Each
about what chemical elements are in the rock. The can acquire and store thousands of full-color images.
tools on the turret at the end of Curiosity’s 7-foot-long Each is also capable of recording high-definition video.
(2.1-meter-long) robotic arm include a radiation-emitting Combining information from the two eyes can yield 3-D
instrument that reads X-ray clues to targets’ composi- views where the images overlap.
tion and a magnifying-lens camera. The arm can deliver
soil and powdered-rock samples to an instrument that Mastcam imaging of the shapes and colors of land-
uses X-ray analysis to identify minerals in the sample scapes, rocks and soils will provide clues about the his-
and to an instrument that uses three laboratory methods tory of environmental processes that have formed them
for assessing carbon compounds and other chemicals and modified them over time. Images and videos of the
important to life and indicative of past and present pro- sky will document contemporary processes, such as the
cesses. For characterizing the modern environment, the movement of clouds and dust.
rover also carries instruments to monitor the weather,
measure natural radiation and seek evidence of water The telephoto Mastcam is called “Mastcam 100” for its
beneath the surface. To provide context for all the other 100-millimeter focal-length lens. Its images cover an area
instruments, a camera will record images of the landing about six degrees wide and five degrees tall, in 1,600 pix-
area during descent. els by 1,200 pixels. This yields a scale of 2.9 inches (7.4
centimeters) per pixel at a distance of about six-tenths of
The 10 science instruments on the Mars Science a mile (1 kilometer) and about 0.006 inch (150 microns)
Laboratory have a combined mass of 165 pounds (75 per pixel at a distance of 6.6 feet (2 meters). The camera
kilograms), compared with a five-instrument science provides enough resolution to distinguish a basketball
payload totaling 11 pounds (5 kilograms) on each of the from a football at a distance of seven football fields, or to
twin rovers, Spirit and Opportunity, that landed on Mars read “ONE CENT” on a penny on the ground beside the
in 2004. The mass of just one of Curiosity’s 10 instru- rover.
ments, 88 pounds (40 kilograms) for Sample Analysis at
Mars, is nearly four times the 23-pound (10.6-kilogram) Its left-eye partner, called “Mastcam 34” for its 34-mil-
total mass of the first Mars rover, 1997’s Sojourner on limeter lens, catches a scene three times wider — about
the Mars Pathfinder mission. 18 degrees wide and 15 degrees tall — on an identical
detector. It can obtain images with 8.7 inches (22 cen-
Assessing past and present habitability of environments timeters) per pixel at a distance of about six-tenths of a
at sites visited by Curiosity will require integrating the mile (1 kilometer) and 0.018 inch (450 microns) per pixel
results of the various instruments, not any single instru- at a distance of 6.6 feet (2 meters).
ment. Science operations and analysis will be coor-
dinated through the Mars Science Laboratory Project The centers of Mastcam’s lenses sit about 6.5 feet (2.0
Science Group, whose members are Project Scientist meters) above ground level. The eyes are farther apart —
John Grotzinger, of the California Institute of Technology, about 10 inches (25 centimeters) — than the stereo eyes
Pasadena, Calif.; Program Scientist Michael Meyer of on earlier Mars surface robots. The cameras can focus
NASA Headquarters, Washington; and the principal on features at any distance from about 6 feet (just under
investigator for each of the following investigations. 2 meters) to infinity.

Mast Camera (Mastcam) When Curiosity drives to a new location, the Mastcam 34
can record a full-color, full-circle panorama showing ev-
Two two-megapixel color cameras on Curiosity’s mast erything from the nearby ground to the horizon by taking
are the left and right eyes of the Mast Camera, or 150 images in about 25 minutes. For a first look, these
Mastcam investigation. These versatile cameras have may be sent to Earth initially as compressed “thumbnail”

Mars Science Laboratory Landing 11 Press Kit
versions. Mastcam thumbnail frames — roughly 150-by- include science spectral filters for examining the ground
150-pixel versions of each image — can be sent as or sky in narrow bands of visible-light or near-infrared
an index of the full-scale images held in the onboard wavelengths. These science filters can be used for
memory. follow-up observations to gain more information about
rocks or other features of interest identified in red-green-
Using the Mastcam 100, the team will be able to see blue images. One additional filter on each camera allows
farther off to the sides of the rover’s path, compared with it to look directly at the sun to measure the amount of
what has been possible with earlier Mars rovers. That dust in the atmosphere, a key part of Mars’ weather.
will help with selection of the most interesting targets to
approach for analyzing with Curiosity’s other instruments Mastcam’s color-calibration target on the rover deck
and will provide additional geological context for inter- includes magnets to keep the highly magnetic Martian
preting data about the chosen targets. dust from accumulating on portions of color chips and
white-gray-balance reference chips. Natural lighting on
The Mastcams will provide still images and video to Mars tends to be redder than on Earth due to dust in
study motions of the rover — both for science, such Mars’ atmosphere. “True color” images can be pro-
as seeing how soils interact with wheels, and for en- duced that incorporate that lighting effect — compa-
gineering, such as aiding in use of the robotic arm. In rable to the warm, orange lighting that is experienced at
other videos, the team may use cinematic techniques sunset on Earth. Alternatively, a white-balance calcula-
such as panning across a scene and using the rover’s tion can be used to adjust for the tint of the lighting, as
movement for “dolly” shots. Video from the cameras is the human eye tends to do and digital cameras can do.
720p high definition at four to seven frames per second, The Mastcams are capable of producing both true-color
depending on exposure time. and white-balanced images.

Malin Space Science Systems, San Diego, built the The Mastcam principal investigator is Michael Malin, a
Mastcams and two of Curiosity’s other science instru- geologist who founded Malin Space Science Systems
ments: the Mars Hand Lens Imager and the Mars and has participated in NASA Mars exploration since the
Descent Imager. Mariner 9 mission in 1971–72.

The four cameras from Malin Space Science Systems Chemistry and Camera (ChemCam)
share several design features. They use a Bayer pattern
filter, as found in many commercial digital cameras, for The investigation using a rock-zapping laser and a tele-
color imaging. Bayer filtering means that the charge- scope mounted atop Curiosity’s mast is the Chemistry
coupled device (CCD) that detects each pixel of the and Camera suite, or ChemCam. It also includes spec-
image is covered with a grid of green, red and blue filters trometers and electronics down inside the rover.
so that the camera gets the three color components
over the entire scene in a single exposure. This is a The laser can hit rock or soil targets up to about 23
change from color cameras on earlier Mars landers and feet (7 meters) away with enough energy to excite a
rovers, which took a series of exposures through differ- pinhead-size spot into a glowing, ionized gas, called
ent filters to be combined into color composites by pro- plasma. The instrument observes that spark with the
cessing on Earth. The filter design used for Curiosity’s telescope and analyzes the spectrum of light to identify
science cameras results in pictures in which the color the chemical elements in the target.
closely mimics the way the average human eye sees the
world. Each of the cameras uses a focusing mechanism The telescope, with a diameter of 4.33 inches (110
from MDA Information Systems Space Division, formerly millimeters), doubles as the optics for the camera of
Alliance Spacesystems, Pasadena, Calif. Each uses ChemCam, which records monochrome images on
a Kodak CCD with an array of 1,600 by 1,200 active a 1,024-pixel-by-1,024-pixel detector. The telescopic
pixels. Each has an eight-gigabyte flash memory. camera, called the remote micro-imager, or RMI, will
show context of the spots hit with the laser. It can also
Besides the affixed red-green-blue filter grid, the be used independently of the laser for observations of
Mastcams have wheels of other color filters that can be targets at any distance.
rotated into place between the lens and the CCD. These

Mars Science Laboratory Landing 12 Press Kit
Information from ChemCam will help researchers survey extreme environments, such as inside nuclear reactors
the rover’s surroundings and choose which targets to and on the sea floor, and has had experimental
approach for study with the tools on the arm and the applications in environmental monitoring and cancer
analytical laboratory instruments. ChemCam can also detection, but ChemCam is its first use in interplanetary
analyze many more targets than those instruments exploration.
can. It can be used on multiple targets the same day,
while the analytical laboratory investigations — SAM Roger Wiens, a geochemist with the U.S. Department
and CheMin — take multiple days per target. It can also of Energy’s Los Alamos National Laboratory in
check the composition of targets inaccessible to the Los Alamos, N.M., is the principal investigator for
rover’s other ingredient-identifying instruments, such as ChemCam. For developing, building and testing the
rock faces beyond the reach of Curiosity’s robotic arm. instrument, Los Alamos partnered with researchers in
France funded by the French national space agency,
The spot hit by ChemCam’s infrared laser gets more Centre National d’Études Spatiales. The deputy prin-
than a million watts of power focused on it for five cipal investigator is Sylvestre Maurice, a spectroscopy
one-billionths of a second. Light from the resulting flash expert with the Institut de Recherche en Astrophysique
comes back to ChemCam through the telescope, then et Planétologie at the Observatoire Midi-Pyrénées,
through about 20 feet (6 meters) of optical fiber down Toulouse, France.
the mast to three spectrometers inside the rover. The
spectrometers record intensity at 6,144 different wave- France provided ChemCam’s laser and telescope. The
lengths of ultraviolet, visible and infrared light (wave- laser was built by Thales, Paris, France. Los Alamos
lengths from 240 to 850 nanometers). Different chemical National Laboratory supplied the spectrometers and
elements in the target, in their ionized state, emit light data processors. The optical design for the spectrome-
at different wavelengths. Dozens of laser pulses on the ters came from Ocean Optics, Dunedin, Fla. NASA’s Jet
same spot will be used to achieve the desired accuracy Propulsion Laboratory, Pasadena, Calif., provided fiber-
in identifying elements. Among the many elements that optic connections linking the two parts of the instru-
the instrument can identify in rocks and soils are sodium, ment and a cooling machine to keep the spectrometers
magnesium, aluminum, silicon, calcium, potassium, cold. The ChemCam team includes experts in mineral-
titanium, manganese, iron, hydrogen, oxygen, beryllium, ogy, geology, astrobiology and other fields, with some
lithium, strontium, nitrogen and phosphorus. members also on other Curiosity instrument teams.

If a rock has a coating of dust or a weathered rind, Alpha Particle X-Ray Spectrometer (APXS)
hundreds of repeated pulses from the laser can remove
those layers to provide a reading of the rock’s interior The Alpha Particle X-Ray Spectrometer (APXS) on
composition and a comparison between the interior and Curiosity’s robotic arm, like its predecessors on the
the coating. arms of all previous Mars rovers, will identify chemical
elements in rocks and soils.
Researchers also plan to use ChemCam to study the
soil at each place Curiosity stops. These observations The APXS instruments on Sojourner, Spirit and
will document local and regional variations in the soil’s Opportunity produced important findings from those
composition and — from images taken through the missions, including salty compositions indicative of a
telescope by the remote micro-imager — in the size wet past in bedrocks examined by Opportunity and
distribution of soil particles. the signature of an ancient hot spring or steam vent in
soil examined by Spirit. The APXS on Curiosity deliv-
Another capability will be to check for water, either ers greater sensitivity, better scheduling versatility and a
bound into mineral composition or as frost. By quickly new mode for optimal positioning.
identifying hydrogen and oxygen, ChemCam can pro-
vide unambiguous identification of water if any is on the The Canadian Space Agency contributed this
surface in the area Curiosity explores. Canadian-made instrument for the Mars Science
Laboratory. A pinch of radioactive material emits radia-
ChemCam uses a technology called laser-induced tion that “queries” the target and an X-ray detector
breakdown spectroscopy. This method of determining “reads” the answer.
the composition of an object has been used in other

Mars Science Laboratory Landing 13 Press Kit
The APXS sensor head, about the size of a cupcake, Additional improvement in sensitivity, mainly for heavy
rides on the multi-tool turret at the end of Curiosity’s arm. elements such as iron, comes from increasing the
The rover will place the spectrometer’s contact-sensing amount X-rays emitted by the curium. Curiosity’s APXS
surface directly onto most rock targets selected for has about 700 micrograms (in mass) or 60 millicuries
APXS readings or just above some soil targets. (in radioactivity), which is twice as much as Spirit’s or
Opportunity’s. Curium is a synthetic element first identi-
The instrument determines the abundance of elements fied in a laboratory in 1944. The specific isotope used in
from sodium to strontium, including the major rock- all Mars rovers’ APXS instruments is curium 244, which
forming and soil-forming elements sodium, magnesium, has a half-life of 18.1 years. This makes it ideal for long-
aluminum, silicon, calcium, iron and sulfur. In 10-minute duration missions, where even after more than seven
quick looks, it can detect even minor ingredients down years of the Opportunity mission, the loss in activity is
to concentrations of about one-half percent. In three- hardly noticeable.
hour readings, it can detect important trace elements
down to concentrations of 100 or fewer parts per million. The additional X-ray intensity will benefit use of a tech-
It has a high sensitivity to salt-forming elements such as nique called the scatter peak method, which was
sulfur, chlorine and bromine, which can indicate interac- developed by physicist Iain Campbell, an APXS co-
tion with water in the past. investigator at the University of Guelph, Ontario, Canada.
This method extracts information about elements invis-
The APXS will characterize the geological context and ible to X-rays, such as oxygen. It was used to detect and
inform choices about acquiring samples for analysis in- quantify water bound in the minerals of salty subsurface
side the mission’s analytical laboratory instruments: SAM soils examined by Spirit at Gusev Crater.
and CheMin. Learning which elements, in what concen-
trations, are in the targets will help researchers identify When the spectrometer is in contact with the target, it
processes that formed the rocks and soils in the area of examines a patch about 0.7 inch (1.7 centimeters) in
Mars where Curiosity is working. diameter. It detects elements to a depth of about 0.0002
inch (5 microns) for low-atomic-weight elements and to
The spectrometer uses the radioactive element curium about 10 times that depth for heavier elements. The dust
as a source to bombard the target with energetic alpha removal tool on Curiosity’s arm turret can be used to
particles (helium nuclei) and X-rays. This causes each el- brush some rock surfaces clean before APXS examines
ement in the target to emit its own characteristic X-rays, them.
which are then registered by an X-ray detector chip
inside the sensor head. The investigation’s main elec- For some soil targets, to avoid pushing the instrument
tronics package, which resides inside the rover, records into the soil, the spectrometer will not be placed in direct
all detected X-rays with their energy and assembles the contact with the target. In those cases, placement will
detections into the X-ray spectrum of this sample. use a standoff distance of about 0.4 inch (1 centimeter)
or less.
On Spirit and Opportunity, the need for the X-ray detec-
tor chip to stay cold, and the length of time necessary Another new feature for Curiosity’s APXS is an autono-
for acquiring a measurement, have restricted most mous placement mode. With this software, as the arm
APXS measurements to Martian nighttime hours. One moves the spectrometer step-by-step closer to the soil,
change in Curiosity’s APXS is the possibility to activate a the instrument checks X-rays from the target for several
solid-state electric cooler for the detector, for use of the seconds at each step. When the count rate reaches a
APXS during Martian daytime. predetermined criterion of what would be adequate for a
good compositional reading, the software knows, “OK.
Curiosity’s APXS can make measurements in about That’s close enough.” The arm’s approach movements
one-third the time needed for equivalent readings by its cease and the longer-duration APXS reading begins. A
predecessors. This improvement in sensitivity results more complex variation of this autonomous placement
mainly from shrinking the distance between the X-ray mode may use brief readings at several positions parallel
detector and the sample by about one-third, to 0.75 to the ground surface, scanning a larger area for certain
inch (19 millimeters). compositional criteria, such as ratio of iron to sulfur, and
quickly selecting the most distinctive spots for longer-
duration readings.

Mars Science Laboratory Landing 14 Press Kit
Besides examining rocks and soils in place, the science lights and adjustable focus. Also, it sits on a longer arm,
team can use the APXS to check processed samples one that can hold MAHLI up higher than the cameras
that the arm places on the rover’s observation tray and on the rover’s mast for seeing over an obstacle or cap-
soil freshly exposed by action of the rover’s wheels. An turing a rover self-portrait.
onboard basaltic rock slab, surrounded by nickel plate,
will be used periodically to check the performance and When positioned at its closest range — about 0.8 inch
calibration of the instrument. (21 millimeters) from its target — the camera’s images
have a resolution of slightly less than one one-thou-
The principal investigator for Curiosity’s APXS is Ralf sandth of an inch (14 microns) per pixel. The field of
Gellert, a physicist at the University of Guelph in Ontario, view for that close-up is a rectangle about 0.9 inch (2.2
Canada. He was part of the team that designed and centimeters) by 0.7 inch (1.7 centimeters).
built the Spirit and Opportunity APXS instruments at
the Max Planck Institute in Mainz, Germany, and pro- The camera can be held at a series of different dis-
vided the new scientific design for the Mars Science tances from a target to show context as well as detail
Laboratory APXS based on the experience gained by adjusting the focus. At about 3 feet (1 meter) from
through the long operation of those predecessors. MDA, a target, it still has a pixel resolution of about 0.02 inch
in Brampton, Ontario, Canada, built the instrument as (half a millimeter) in a view covering an area about 2 feet
the prime contractor for the Canadian Space Agency. (70 centimeters) wide. By manipulation of arm position
and focus, the camera can be used to examine hard-
Mars Hand Lens Imager (MAHLI) ware on the rover or record time-lapse views of activi-
ties such as opening a sample inlet cover.
The Mars Hand Lens Imager, or MAHLI, is a focusable
color camera on the tool-bearing turret at the end of MAHLI has two sets of white light-emitting diodes to
Curiosity’s robotic arm. Researchers will use it for magni- enable imaging at night or in deep shadow. Two other
fied, close-up views of rocks and soils, and also for light-emitting diodes on the instrument glow at the ultra-
wider scenes of the ground, the landscape or even the violet wavelength of 365 nanometers. These will make it
rover. Essentially, it is a hand-held camera with a macro possible to check for materials that fluoresce under this
lens and autofocus. illumination.

The investigation takes its name from the type of hand Malin Space Science Systems, San Diego, developed,
lens magnifying tool that every field geologist carries for built and operates MAHLI. This camera shares some
seeing details in rocks. Color, crystal shapes, mineral traits with three other cameras on Curiosity from the
cleavage planes and other visible details from such same company. It uses a red-green-blue filter grid like
close-up observation provide clues to a rock’s composi- the one on commercial digital cameras for obtaining a
tion. In sedimentary rocks, the sizes and shapes of the full-color image with a single exposure. Its image detec-
grains in the rock, and the scale of fine layering, provide tor is a charge-coupled device with an array of 1,600 by
information about how the grains were transported 1,200 active pixels. It stores images in an eight-gigabyte
and deposited. Sharp-edge grains have not been worn flash memory, and it can perform an onboard focus
down by tumbling long distances, for example. The size merge of eight images to reduce from eight to two the
of grains can indicate whether the water or wind that number of images returned to Earth in downlink-limited
carried them was moving quickly or not. situations.

These clues garnered from MAHLI images can aid both Curiosity carries a vertically mounted calibration target
in selection of which targets to analyze with other instru- for MAHLI, for checking color, white balance, resolution,
ments and in directly reading the environmental history focus and the ultraviolet illumination.
recorded in the rocks and soils the rover encounters.
Ken Edgett of Malin Space Science Systems, a ge-
As a close-up magnifying camera, MAHLI resembles ologist who has helped run cameras on several Mars
the Microscopic Imager instrument mounted at the orbiters, is the principal investigator for MAHLI. A unified
end of the robotic arm on each of the twin Mars rovers imaging-science team for the three Malin-supplied in-
Spirit and Opportunity. MAHLI has significantly greater struments combines experience in geologic field work,
capabilities than those predecessors, however: full color, Mars exploration and space cameras.

Mars Science Laboratory Landing 15 Press Kit
Chemistry and Mineralogy (CheMin) the instrument. The other 27 are reusable holders for
Martian samples.
The Chemistry and Mineralogy experiment, or CheMin,
is one of two investigations that will analyze powdered Each pair of cells is mounted on a metal holder that re-
rock and soil samples delivered by Curiosity’s robotic sembles a tuning fork. A tiny piezoelectric buzzer excites
arm. It will identify and quantify the minerals in the the fork to keep the particles in the sample moving inside
samples. Minerals provide a durable record of past the cell during analysis of the sample. This puts the par-
environmental conditions, including information about ticles in a random mix of orientations to the X-ray beam,
possible ingredients and energy sources for life. improving detection of how the mineral crystals in the
sample scatter the X-rays. The piezoelectric vibration,
CheMin uses X-ray diffraction, a first for a mission to at about 200 cycles per second (middle C on a piano
Mars. This is a more definitive method for identifying is 261 cycles per second) also helps keep the powder
minerals than was possible with any instrument on previ- flowing during filling and dumping of the cell.
ous missions. The investigation supplements the diffrac-
tion measurements with X-ray fluorescence capability to CheMin generates X-rays by aiming high-energy elec-
determine further details of composition by identifying trons at a target of cobalt. The X-rays emitted by the
ratios of specific elements present. cobalt are then directed into a narrow beam. During
analysis, the sample sits between the incoming beam
X-ray diffraction works by directing an X-ray beam at on one side and the instrument’s detector on the other.
a sample and recording how X-rays are scattered by The detector is a charge-coupled device like the ones in
the sample at the atomic level. All minerals are crystal- electronic cameras, but sensitive to X-ray wavelengths
line, and in crystalline materials, atoms are arranged and cooled to minus 76 degrees Fahrenheit (minus 60
in an orderly, periodic structure, causing the X-rays to degrees Celsius).
be scattered at predictable angles. From those angles,
researchers can deduce the spacing between planes Each CheMin analysis of a sample requires up to
of atoms in the crystal. Each different mineral yields a 10 hours of accumulating data while the X-rays are
known, characteristic series of spacings and intensities, hitting the sample. The time may be split into two or
its own fingerprint. more Martian nights of operation.

On Curiosity’s deck, near the front of the rover, one fun- The X-ray diffraction data show the angles at which the
nel with a removable cover leads through the deck top primary X-rays from the beam are deflected and the
to the CheMin instrument inside the rover. The instru- intensity at each angle. The detector also reads second-
ment is a cube about 10 inches (25 centimeters) on ary X-rays emitted by the sample itself when it is excited
each side, weighing about 22 pounds (10 kilograms). by the primary X-rays. This is the X-ray fluorescence
information. Different elements emit secondary X-rays at
The rover acquires rock samples with a percussive drill different frequencies. CheMin’s X-ray fluorescence capa-
and soil samples with a scoop. A sample processing bility can detect elements with an atomic number greater
tool on the robotic arm puts the powdered rock or soil than 11 (sodium) in the periodic table.
through a sieve designed to remove any particles larger
than 0.006 inch (150 microns) before delivering the ma- Instruments that previous missions to Mars have used
terial into the CheMin inlet funnel. Vibration helps move for studying Martian minerals have not been able to
the sample material — now a gritty powder — down provide definitive identification of all types of minerals.
the funnel. Each sample analysis will use about as much CheMin will be able to do so for minerals present in
material as in a baby aspirin. samples above minimal detection limits of about 3 per-
cent of the sample composition. The instrument will also
The funnel delivers the sample into a disc-shaped cell, indicate the approximate concentrations of different min-
about the diameter of a shirt button and thickness of a erals in the sample. X-ray fluorescence can add informa-
business card. The walls of the sample cell are transpar- tion about the ratio of elements in types of minerals with
ent plastic. Thirty-two of these cells are mounted around variable elemental composition, such as the proportion
the perimeter of a sample wheel. Rotating the wheel can of iron to magnesium in iron magnesium silicate (olivine).
position any cell into the instrument’s X-ray beam. Five It can also aid in identifying non-crystalline ingredients in
cells hold reference samples from Earth to help calibrate a sample, such as volcanic glass.

Mars Science Laboratory Landing 16 Press Kit
Each type of mineral forms under a certain set of SAM’s analytical tools fit into a microwave-oven-size box
environmental conditions: the chemistry present (includ- inside the front end of the rover. While it is the biggest
ing water), the temperature and the pressure. Thus, of the 10 instruments on Curiosity, this tightly packed
CheMin’s identification of minerals will provide informa- box holds instrumentation that would take up a good
tion about the environment at the time and place where portion of a laboratory room on Earth. One focus during
the minerals in the rocks and soils formed or were al- development was power efficiency. For example, the
tered. Some minerals the instrument might detect, such two ovens can heat powdered samples to about 1,800
as phosphates, carbonates, sulfates and silica, can degrees Fahrenheit (1,000 degrees Celsius) drawing a
help preserve biosignatures. Whether or not the mission maximum power of just 40 watts. More than a third of a
determines that the landing area has offered a favorable mile (more than 600 meters) of wiring is inside SAM.
habitat for life, the inventory of minerals identified by
CheMin will provide information about processes in the SAM can detect a fainter trace of organics and identify
evolution of the planet’s environment. a wider variety of them than any instrument yet sent to
Mars. It also can provide information about other ingredi-
David Blake, an expert in cosmochemistry and exobiol- ents of life and clues to past environments.
ogy at NASA’s Ames Research Center, Moffett Field,
Calif., is the principal investigator for CheMin. He began One of SAM’s tools, a mass spectrometer like those
work in 1989 on a compact X-ray diffraction instrument seen in many TV crime-solving laboratories, identifies
for use in planetary missions. His work with colleagues gases by the molecular weight and electrical charge of
has resulted in commercial portable instruments for use their ionized states. It will check for several elements
in geological field work on Earth, as well as the CheMin important for life as we know it, including nitrogen, phos-
investigation. The spinoff instruments have found ap- phorous, sulfur, oxygen, hydrogen and carbon.
plications in screening for counterfeit pharmaceuticals in
developing nations and in analyzing archaeological finds. Another tool, a tunable laser spectrometer, uses absorp-
tion of light at specific wavelengths to measure concen-
NASA Ames Research Center won the 2010 Com- trations of methane, carbon dioxide and water vapor.
mercial Invention of the Year Award from NASA for the It also identifies the proportions of different isotopes in
tuning-fork powder vibration system used on CheMin. those gases. Isotopes are variants of the same element
Blake and Philippe Sarazin of inXitu Inc., Campbell, with different atomic weights, such as carbon-13 and
Calif., a co-investigator on the CheMin team, developed carbon-12, or oxygen-18 and oxygen-16. Ratios of
the technology while Sarazin was working as a post- isotopes can be signatures of planetary processes,
doctoral fellow at Ames. such as how Mars might have lost much of its former
atmosphere.
Sample Analysis at Mars (SAM)
The suite’s third analytical tool, a gas chromatograph,
The Sample Analysis at Mars investigation, or SAM, will separates different gases from a mixture to aid identifi-
use a suite of three analytical tools inside Curiosity to cation. It detects organic compounds exiting a capillary
study chemistry relevant to life. One key job is check- column, and then it feeds the separated fractions to the
ing for carbon-based compounds that on Earth are mass spectrometer for a more definitive identification.
molecular building blocks of life. It will also examine the
chemical state of other elements important for life, and SAM also includes a sample manipulation system, and
it will assess ratios of different atomic weights of certain a chemical separation and processing laboratory to sup-
elements for clues about planetary change and ongoing port the analytical tools. The sample manipulation sys-
processes. tem maneuvers 74 sample cups, each about one-sixth
of a teaspoon (0.78 cubic centimeter) in volume. The
SAM will examine gases from the Martian atmosphere chemical separation and processing laboratory includes
and gases that ovens and solvents pull from powdered pumps, tubing, carrier-gas reservoirs, pressure monitors,
rock and soil samples. Curiosity’s robotic arm will deliver ovens, temperature monitors and other components.
the powdered samples to one of two inlet funnels on the Fifty-two specially designed microvalves direct the flow of
rover deck. Atmospheric samples enter through filtered gas through the system. Two soft-drink-can-size vacuum
inlet ports on the side of the rover. pumps rotate 100,000 times per minute to allow all three
instruments to operate at their optimal pressures.

Mars Science Laboratory Landing 17 Press Kit
SAM’s analysis of material from Martian rocks or soils whether any organics close enough to the surface for
begins after powder collected and processed by tools Curiosity to reach them can persist in the harsh condi-
on the arm is dropped into one of SAM’s two solid-sam- tions there without the carbon in them transforming into
ple inlets while the inlet’s protective cover is open. The a more polymerized state.
inlet tubes are highly polished funnels that vibrate to get
the powder to fall into a reusable sample cup. NASA’s investigation of organics on Mars began with
the twin Viking landers in 1976. The original reports from
Fifty-nine of the instrument’s 74 cups are quartz that Viking came up negative for organics. SAM renews the
can be heated to very high temperatures. The sample search with three advantages.
manipulation system pushes the quartz cup holding
the powder into an oven that heats it to about 1,800 The first is Curiosity’s access. Mars is diverse, not
degrees Fahrenheit (about 1,000 degrees Celsius). That uniform. Copious information gained from Mars orbiters
process releases gas from the sample at various tem- in recent years has enabled the choice of a landing site
peratures, depending on the chemistry of the sample. with favorable attributes, such as exposures of clay and
The mass spectrometer measures the release continu- sulfate minerals good at entrapping organic chemicals.
ously. Some of the gas goes to the tunable laser spec- Mobility helps too, especially with the aid of high-resolu-
trometer for measurement of isotopes. Some goes to tion geologic mapping generated from orbital observa-
a trap that concentrates any organics, then to the gas tions. The stationary Viking landers could examine only
chromatograph and mass spectrometer. After use, the what their arms could reach. Curiosity can use mapped
quartz cup can be baked to prepare it for re-use with geologic context as a guide in its mobile search for
another sample. organics and other clues about habitable environments.
Additionally, SAM will be able to analyze samples from
Six of the cups hold calibration solids. SAM also carries more protected interiors of rocks drilled into by Curiosity,
samples of gases for calibration. rather than being restricted to soil samples, as Viking
was.
Nine of the cups are for using a solvent method called
derivatization, rather than high temperature, to pull gases Second, SAM has improved sensitivity, with a capability
from samples of Martian rocks and soils. If the mis- to detect organic compounds at parts per billion levels
sion finds a site rich in organics, this method could be over a wider mass range of molecules and after heating
used to identify larger and more reactive organic mol- samples to a higher temperature.
ecules than is possible with the high-heat method. Each
derivatization cup contains a mixture of a solvent and a Third, the derivatization method for assessing organ-
chemical that, after it reacts with a compound of interest, ics in some SAM samples can reveal a wider range of
turns it into a more volatile compound that can be sepa- organic compounds than was possible with the Viking
rated in the gas chromatograph. These chemicals are experiment. In doing so, it can also check a recent hy-
entirely sealed in with a foil cover. For analysis of sample pothesis that a reactive chemical recently discovered in
powder from a Martian rock or soil by this method, the Martian soil — perchlorate — may have masked organ-
sample manipulation system punctures the foil and adds ics in soil samples baked during Viking tests.
the powder to the liquid in the cup, and the oven heats
the sample to a modest temperature to let the reactions If SAM does not detect any organics, that would be
proceed rapidly. useful information about the unfavorable conditions for
life near the Martian surface. Future missions might look
Curiosity’s “follow the carbon” investigation of organic deeper.
compounds begins as a check for whether any are pres-
ent. Although organic molecules are not, in themselves, If SAM does detect organics, one challenge will be
evidence of life, life as we know it cannot exist without to confirm that these molecules are truly Martian, not
them. Their presence would be important evidence stowaways from Earth carried to Mars on Curiosity. The
both about habitability and about the site’s capability for rover carries five encapsulated bricks of organic check
preserving evidence of life. Meteorites bearing organic material to enable control experiments. The check
compounds have pelted Mars, as well as Earth, for material is a silicon-dioxide ceramic laced with small
billions of years. Uncertainty remains, however, about amounts of synthetic fluorinated organic chemicals not

Mars Science Laboratory Landing 18 Press Kit
found in nature on Earth and not expected on Mars. states and Europe to develop, build and test SAM after
The basic control experiment will collect a powdered NASA selected his team’s proposal for it in 2004.
sample from an organic check brick with the same
drilling, processing and delivery system used for collect- NASA Goddard Space Flight Center built and tested
ing samples from Martian rocks, and then will ana- SAM. France’s space agency, Centre National d’Études
lyze the sample with SAM. If SAM finds any organics Spatiales, provided support to French researchers who
other than the fluorine-containing markers, they will be developed SAM’s gas chromatograph. NASA’s Jet
stowaway suspects. If only the markers are detected, Propulsion Laboratory, Pasadena, Calif., provided the
that would verify that organic-detection is working and tunable laser spectrometer. Honeybee Robotics, New
that the sample-acquisition and handling pathway has York, designed SAM’s sample manipulation system.
passed a test of being clean of organic stowaways.
That control experiment can assess characteristics of Rover Environmental Monitoring Station (REMS)
organic contamination at five different times during the
mission, using the five bricks of organic check material. The Rover Environmental Monitoring Station, or REMS,
Researchers have a variety of tools at their disposal to will record information about daily and seasonal chang-
distinguish organic compounds present in Mars soils es in Martian weather.
and rocks from trace levels of organic compounds from
Earth that might make their way into these samples. This investigation will assess wind speed, wind direction,
air pressure, relative humidity, air temperature, ground
If organic chemicals are present in Martian samples, temperature and ultraviolet radiation. Operational plans
SAM’s inventory of the types and mixtures may provide call for taking measurements for at least five minutes
clues to their origin. For example, organics delivered every hour of the full-Martian-year (98-week) mission.
by meteorites without involvement of biology come
with more random chemical structures than the pat- Spain provided this instrument for the Mars Science
terns seen in mixtures of organic chemicals produced Laboratory.
by organisms. Patterns, such as a predominance of
molecules with an even number of carbon atoms, could Information about wind, temperatures and humidity
be suggestive of biological origin. The derivatization comes from electronic sensors on two finger-like booms
process also allows searching for specific classes of extending horizontally from partway up the main vertical
organics with known importance to life on Earth. For mast holding the ChemCam laser and the Mastcam.
example, it can identify amino acids, the chain links of Each of the booms holds a sensor for recording air tem-
proteins. While these clues may not add up to a defini- perature and three sensors for detecting air movement
tive case either for or against biological origin, they could in three dimensions. Placement of the booms at an
provide important direction for future missions. angle of 120 degrees from each other enables calculat-
ing the velocity even when the main mast is blocking the
Methane is one of the simplest organic molecules. wind from one direction. The boom pointing toward the
Observations from Mars orbit and from Earth in recent front of the rover, Boom 2, also holds the humidity sen-
years have suggested transient methane in Mars’ atmo- sor inside a downward-tilted protective cylinder. Boom
sphere, which would mean methane is being actively 1, pointing to the side and slightly toward the rear, holds
added and then removed from the atmosphere of Mars. an infrared sensor for measuring ground temperature.
With SAM’s tunable laser spectrometer, researchers will
check to confirm whether methane is present, moni- The pressure sensor sits inside the rover body, con-
tor any changes in its concentration, and look for clues nected to the external atmosphere by a tube to a small,
about whether Mars methane is produced by biological dust-shielded opening on the deck. Electronics control-
activity or by processes that do not require life. ling REMS are also inside the rover body.

The principal investigator for SAM is Paul Mahaffy, The ultraviolet sensor is on the rover deck. It measures
a chemist at NASA’s Goddard Space Flight Center, six different wavelength bands in the ultraviolet por-
Greenbelt, Md. He is a veteran of using spacecraft tion of the electromagnetic spectrum, including wave-
instruments to study planetary atmospheres. Mahaffy lengths also monitored from above by NASA’s Mars
has coordinated work of hundreds of people in several Reconnaissance Orbiter. No previous mission to the

Mars Science Laboratory Landing 19 Press Kit
surface of Mars has measured the full ultraviolet spec- The team plans to post daily weather reports from
trum of radiation. Curiosity. Air temperature around the rover mast will
likely drop to about minus 130 degrees Fahrenheit
The REMS investigation will strengthen understanding (about minus 90 degrees Celsius) on some winter nights
about the global atmosphere of Mars and contribute to and climb to about minus 22 Fahrenheit (about minus
the mission’s evaluation of habitability. 30 Celsius) during winter days. In warmer seasons,
afternoon air temperature could reach a balmy
The data will provide a way to verify and improve atmo- 32 Fahrenheit (0 degrees Celsius).
sphere modeling based mainly on observations from
Mars orbiters. For example, significant fractions of the Radiation Assessment Detector (RAD)
Martian atmosphere freeze onto the ground as a south
polar carbon-dioxide ice cap during southern winter and The Radiation Assessment Detector, or RAD, investi-
as a north polar carbon-dioxide ice cap during northern gation on Curiosity monitors high-energy atomic and
winter, returning to the atmosphere in each hemisphere’s subatomic particles coming from the sun, from distant
spring. At Curiosity’s landing site, far from either pole, supernovae and other sources. These particles consti-
REMS will check whether seasonal patterns of changing tute naturally occurring radiation that could be harmful
air pressure fit the existing models for effects of the com- to any microbes near the surface of Mars or to astro-
ing and going of polar carbon-dioxide ice. nauts on a future Mars mission.

Monitoring ground temperature with the other weather RAD’s measurements will help fulfill the Mars Science
data could aid in assessment of whether conditions have Laboratory mission’s key goals of assessing whether
been favorable for microbial life. Even in the extremely Curiosity’s landing region has had conditions favor-
low-humidity conditions anticipated in the landing area, able for life and for preserving evidence about life. This
the combination of ground temperature and humidity investigation also has an additional job. Unlike the rest
information could provide insight about the interaction of of the mission, RAD has a special task and funding from
water vapor between the soil and the atmosphere. If the the part of NASA that is planning human exploration
environment supports, or ever supported, any under- beyond Earth orbit. It will aid design of human missions
ground microbes, that interaction could be crucial. by reducing uncertainty about how much shielding
from radiation future astronauts will need. RAD is mak-
Ultraviolet radiation can also affect habitability. The ul- ing measurements during the trip from Earth to Mars,
traviolet measurements by REMS will allow scientists to supplementing those it will make during Curiosity’s
better predict the amount of ultraviolet light that reaches roving on Mars, because radiation levels in interplan-
Mars’ surface globally in the present and past. Ultraviolet etary space are also important in the design of human
light is destructive to organic material and the reason missions.
that sunscreen is worn on Earth.
The 3.8-pound (1.7-kilogram) RAD instrument has a
The principal investigator for REMS is Javier Gómez- wide-angle telescope looking upward from the hard-
Elvira, an aeronautical engineer with the Center for ware’s position inside the left-front area of the rover.
Astrobiology (Centro de Astrobiología), Madrid, Spain. The telescope has detectors for charged particles with
The center is affiliated with the Spanish National masses up to that of an iron ion. RAD can also de-
Research Council (Consejo Superior de Investigaciones tect neutrons and gamma rays coming from the Mars
Científicas) and the National Institute for Aerospace atmosphere above or the Mars surface material below
Technology (Instituto Nacional de Técnica Aerospacial). the rover.
Spain’s Ministry of Science and Innovation (Ministerio de
Ciencia e Innovación) and Spain’s Center for Industrial Galactic cosmic rays make up one type of radiation that
Technology Development (Centro para el Desarrollo RAD monitors. These are a variable shower of charged
Tecnológico Industrial) supplied REMS. The Finnish particles coming from supernova explosions and other
Meterological Insitute developed the pressure sensor. events extremely far from our solar system.

To develop the instrument and prepare for analyzing The sun is the other main source of energetic particles
the data it will provide, Spain has assembled a team of that this investigation detects and characterizes. The
about 40 researchers — engineers and scientists. sun spews electrons, protons and heavier ions in “solar

Mars Science Laboratory Landing 20 Press Kit
particle events” fed by solar flares and ejections of mat- watch so that it can catch any rare but vitally important
ter from the sun’s corona. Astronauts might need to solar particle events.
move into havens with extra shielding on an interplan-
etary spacecraft or on Mars during solar-particle events. The first science data from the mission have come from
RAD’s measurements during the trip from Earth to Mars.
Earth’s magnetic field and atmosphere provide effective These en-route measurements are enabling correlations
shielding against the possible deadly effects of galac- with instruments on other spacecraft that monitor solar
tic cosmic rays and solar particle events. Mars lacks particle events and galactic cosmic rays in Earth’s neigh-
a global magnetic field and has only about 1 percent borhood and also are yielding data about the radiation
as much atmosphere as Earth does. Just to find high- environment farther from Earth.
enough radiation levels on Earth for checking and cali-
brating RAD, the instrument team needed to put it inside RAD’s principal investigator is physicist Don Hassler
major particle-accelerator research facilities in the United of the Southwest Research Institute’s Boulder, Colo.,
States, Europe, Japan and South Africa. branch. His international team of co-investigators
includes experts in instrument design, astronaut safety,
The radiation environment at the surface of Mars has atmospheric science, geology and other fields.
never been fully characterized. NASA’s Mars Odyssey
orbiter, which reached Mars in 2001, assessed radiation Southwest Research Institute in Boulder and in San
levels above the Martian atmosphere with an investiga- Antonio, together with Christian Albrechts University in
tion named the Mars Radiation Environment Experiment. Kiel, Germany, built RAD with funding from the NASA
Current estimates of the radiation environment at the Exploration Systems Mission Directorate and Germany’s
surface rely on modeling of how the thin atmosphere national aerospace research center, Deutsches Zentrum
affects the energetic particles, but uncertainty in the für Luft- und Raumfahrt.
modeling remains large. A single energetic particle hitting
the top of the atmosphere can break up into a cascade Measurements of ultraviolet radiation by Curiosity’s
of lower-energy particles that might be more damaging Rover Environmental Monitoring Station will supplement
than a single high-energy particle. RAD’s measurements of other types of radiation.

In addition to its precursor role for human exploration, Dynamic Albedo of Neutrons (DAN)
RAD will contribute to the mission’s assessment of
Mars’ habitability for microbes and search for organics. The Dynamic Albedo of Neutrons investigation, or DAN,
Radiation levels probably make the surface of modern can detect water bound into shallow underground min-
Mars inhospitable for microbial life and would con- erals along Curiosity’s path.
tribute to the breakdown of any near-surface organic
compounds. The measurements from RAD will feed The DAN instrument shoots neutrons into the ground
calculations of how deeply a possible future robot on a and measures how they are scattered, giving it a high
life-detection mission might need to dig or drill to reach a sensitivity for finding any hydrogen to a depth of about
microbial safe zone. For assessing whether the surface 20 inches (50 centimeters) directly beneath the rover.
radiation environment could have been hospitable for
microbes in Mars’ distant past, researchers will combine The Russian Federal Space Agency contributed DAN
RAD’s measurements with estimates of how the activity to NASA as part of a broad collaboration between the
of the sun and the atmosphere of Mars have changed in United States and Russia in the exploration of space.
the past few billion years.
The instrument can be used in reconnaissance to iden-
Radiation levels in interplanetary space vary on many tify places for examination with Curiosity’s other tools.
time scales, from much longer than a year to shorter Also, rock formations that Curiosity’s cameras view at
than an hour. Assessing the modern radiation environ- the surface may be traced underground by DAN, ex-
ment on the surface will not come from a one-time set of tending scientists’ understanding of the geology.
measurements. Operational planning for Curiosity antici-
pates that RAD will record measurements for 15 minutes DAN will bring to the surface of Mars an enhancement
of every hour throughout the prime mission, on steady of nuclear technology that has already detected Martian

Mars Science Laboratory Landing 21 Press Kit
water from orbit. “Albedo” in the investigation’s name goes with the Martian seasons, such as soil moisture
means reflectance — in this case, how high-energy that varies with the atmospheric humidity. Together
neutrons injected into the ground bounce off of atomic with Curiosity’s cameras and weather station, DAN will
nuclei in the ground. Neutrons that collide with hydro- observe how the sparse water cycle on Mars works in
gen atoms bounce off with a characteristic decrease in the present. DAN also could detect any water ice in the
energy, like one billiard ball hitting another. By measuring shallow subsurface, a low probability at Curiosity’s Gale
the energies of the reflected neutrons, DAN can detect Crater landing site.
the fraction that was slowed in these collisions, and
therefore the amount of hydrogen. Operational planning anticipates using DAN during short
pauses in drives and while the rover is parked. It will
Oil prospectors use this technology in instruments check for any changes or trends in subsurface hydro-
lowered down exploration holes to detect the hydrogen gen content from place to place along the traverse.
in petroleum. Space explorers have adapted it for mis-
sions to the moon and Mars, where most hydrogen is in Russia’s Space Research Institute developed the DAN
water ice or in water-derived hydroxyl ions. instrument in close cooperation with the N.L. Dukhov
All-Russia Research Institute of Automatics, Moscow,
DAN Principal Investigator Igor Mitrofanov of Space and the Joint Institute of Nuclear Research, Dubna.
Research Institute, Moscow, is also the principal in-
vestigator for a Russian instrument on NASA’s Mars Mars Descent Imager (MARDI)
Odyssey orbiter, the high-energy neutron detector,
which measures high energy of neutrons coming During the final few minutes of Curiosity’s flight to the
from Mars. In 2002, it and companion instruments on surface of Mars, the Mars Descent Imager, or MARDI,
Odyssey detected hydrogen interpreted as abundant will record a full-color video of the ground below. This
underground water ice close to the surface at high will provide the Mars Science Laboratory team with in-
latitudes. formation about the landing site and its surroundings, to
aid interpretation of the rover’s ground-level views and
The neutron detectors on Odyssey rely on galactic cos- planning of initial drives. Hundreds of the images taken
mic rays hitting Mars as a source of neutrons. DAN can by the camera will show features smaller than what can
work in a passive mode relying on cosmic rays, but it be discerned in images taken from orbit.
also has its own pulsing neutron generator for an active
mode of shooting high-energy neutrons into the ground. The video will also give fans worldwide an unprecedent-
In active mode, it is sensitive enough to detect water ed sense of riding a spacecraft to a landing on Mars.
content as low as one-tenth of 1 percent in the ground
beneath the rover. MARDI will record the video on its own 8-gigabyte flash
memory at about four frames per second and close to
The neutron generator is mounted on Curiosity’s right 1,600 by 1,200 pixels per frame. Thumbnails and a few
hip, a pair of neutron detectors on the left hip. Pulses samples of full-resolution frames will be transmitted to
last about 1 microsecond and repeat as frequently as Earth in the first few days after landing. The nested set
10 times per second. The detectors measure the flow of of images from higher altitude to ground level will enable
moderated neutrons with different energy levels return- pinpointing of Curiosity’s location. The pace of sending
ing from the ground, and their delay times. Neutrons the rest of the frames for full-resolution video will de-
that arrive later may indicate water buried beneath a pend on sharing priority with data from the rover’s other
drier soil layer. The generator will be able to emit a total investigations.
of about 10 million pulses during the mission, with about
10 million neutrons at each pulse. The full video — available first from the thumbnails in
YouTube-like resolution and later in full detail — will
The most likely form of hydrogen in the ground of the begin with a glimpse of the heat shield falling away from
landing area is hydrated minerals. These are minerals beneath the rover. The first views of the ground will
with water molecules or hydroxyl ions bound into the cover an area several kilometers (a few miles) across.
crystalline structure of the mineral. They can tenaciously Successive frames taken as the vehicle descends will
retain water from a wetter past when all free water has close in and cover successively smaller areas. The video
gone. DAN may also detect water that comes and will likely nod up and down to fairly large angles owing

Mars Science Laboratory Landing 22 Press Kit
to parachute-induced oscillations. Its roll clockwise and corded field of view of 70 degrees by 55 degrees. From
counterclockwise will be smaller, as thrusters on the an altitude of 1.2 miles (2 kilometers) during descent that
descent stage control that motion. When the parachute will provide a resolution of about 5 feet (1.5 meters) per
is jettisoned, the video will show large angular motions pixel, though swinging and shaking of the spacecraft will
as the descent vehicle maneuvers to avoid re-contacting likely blur some frames despite a fast (1.3 millisecond)
the back shell and parachute. Rocket engine vibration exposure time.
may also be seen. A few seconds before landing, the
rover will be lowered on tethers beneath the descent Color information comes from a Bayer pattern filter ar-
stage, and the video will show the relatively slow ap- ray, as used in many commercial digital cameras. The
proach to the surface. The final frames, after landing, will camera’s CCD is covered with a grid of green, red and
cover a bath-towel-size patch of ground under the front- blue filters so that each exposure samples all of those
left corner of the rover. colors throughout the field of view. A piece of white
material on the inside surface of the heat shield will serve
Besides the main objective of providing geologic context as a white-balance target as the heat shield falls away at
for the observations and operations of the rover during the beginning of the recorded descent video.
the early part of mission on Mars, MARDI will provide
insight about Mars’ atmosphere. Combining informa- Malin Space Science Systems also provided descent
tion from the descent images with information from the imagers for NASA’s Mars Polar Lander, launched in
spacecraft’s motion sensors will allow for calculating 1999, and Phoenix Mars Lander, launched in 2007.
wind speeds affecting the spacecraft on its way down, However, the former craft was lost during its landing and
an important atmospheric science measurement. The the latter did not use its descent imager due to concern
descent data will later aid in designing and testing future about the spacecraft’s data-handling capabilities during
landing systems for Mars that could add more control for crucial moments just before landing.
hazard avoidance.
Engineering Instruments
Throughout Curiosity’s mission on Mars, MARDI will offer
the capability to obtain images of ground beneath the Some of the tools that primarily serve engineering
rover at resolutions down to 0.06 inch (1.5 millimeters) purposes on Mars Science Laboratory will also gener-
per pixel, for precise tracking of its movements or for ate information useful to scientific understanding about
geologic mapping. The science team will decide whether Mars. Most of these, including the engineering cameras
or not to use that capability. Each day of operations on and the drill, are described in the spacecraft section
Mars will require choices about how to budget power, of this document. One set of instruments carried on
data and time. the heat shield of the spacecraft’s entry vehicle serves
specifically to gather data about the Martian atmosphere
Malin Space Science Systems, San Diego, provided and performance of the heat shield for use in design-
MARDI, as well as three other cameras on Curiosity: ing future systems for descending through planetary
the Mast Camera pair and the Mars Hand Lens Imager. atmospheres.
Michael Malin is the principal investigator for MARDI,
which shares a unified imaging-science team with the MSL Entry, Descent and Landing Instrument
other two instruments from his company. (MEDLI) Suite

MARDI consists of two parts: the wide-angle camera A set of sensors attached to the heat shield of the Mars
mounted toward the front of the port side of Curiosity Science Laboratory (MSL) is collectively named the MSL
and a digital electronics assembly inside the warm Entry, Descent and Landing Instrument (MEDLI) Suite.
electronics box of the rover’s chassis. The instrument’s MEDLI will take measurements eight times per second
electronics, including the 1,600-pixel-by-1,200-pixel during the period from about 10 minutes before the ve-
charge-coupled device (CCD) in the camera, are the hicle enters the top of the Martian atmosphere until after
same design as used in the Mast Camera and Mars the parachute has opened, about four minutes after
Hand Lens Imager. entry. The measurements will be analyzed for informa-
tion about atmospheric conditions and performance of
The rectangular field of the CCD sits within a 90-degree the entry vehicle.
circular field of view of the camera lens, yielding a re-

Mars Science Laboratory Landing 23 Press Kit
Due to the mass of the entry vehicle (5,359 pounds, or MEDLI consists of seven pressure sensors (Mars entry
2,431 kilograms, after jettison of the spacecraft’s cruise atmospheric data system sensor, or MEADS), seven
stage), the diameter of its heat shield (14.8 feet, or 4.5 plugs with multiple temperature sensors (Mars inte-
meters) and the speed at which the vehicle will enter grated sensor plug, or MISP) and a support electronics
the atmosphere (about 13,200 mph, or 5,900 meters box. Data from the entry vehicle’s inertial measurement
per second), the heating and stress on the heat shield unit, which senses changes in velocity and direction,
will be the highest ever for an entry vehicle at Mars. will augment the MEDLI data. Each of the temperature-
Experience gained with this mission will aid planning for sensing plugs has thermocouples to measure tempera-
potential future missions that could be even heavier and tures at four different depths in the heat shield’s thermal
larger, such as would be necessary for a human mission protection tiles, plus a sensor to measure the rate at
to Mars. which heat shield material is removed due to atmo-
spheric entry heating.
Models of the Martian atmosphere, heating environ-
ments, vehicle aerodynamics, and heat-shield per- Analysis of data from the pressure sensors and iner-
formance, among other factors, were employed in tial measurement unit will provide an altitude profile of
designing the Mars Science Laboratory entry vehicle. atmospheric density and winds, plus information about
Uncertainties in these parameters must also be mod- pressure distribution on the heat shield surface, orienta-
eled. To account for those uncertainties, the design tion of the entry vehicle and velocity. Data from the tem-
incorporates large margins for success. The margin perature sensors will be used to evaluate peak heating,
comes at a cost of additional mass. The goal of MEDLI distribution of heating over the heat shield, turbulence
is to better quantify these atmospheric entry character- in the flow of gas along the entry vehicle’s surface, and
istics and possibly reduce unnecessary mass on future in-depth performance of the heat shield material.
Mars missions, by collecting data on the performance
of the Mars Science Laboratory entry vehicle during its NASA’s Exploration Systems Mission Directorate (which
atmospheric entry and descent. has responsibility for planning human missions be-
yond Earth orbit) and Aeronautics Research Mission
Directorate (which invests in fundamental research
of atmospheric flight) have funded MEDLI. F. McNeil
Cheatwood of NASA’s Langley Research Center,
Hampton, Va., is the principal investigator for MEDLI.
Deputy principal investigator is Michael Wright of
NASA’s Ames Research Center, Moffett Field, Calif.

Mars Science Laboratory Landing 24 Press Kit
Mission Overview
NASA’s Mars Science Laboratory mission will put a One priority for choice of a launch period within the
mobile laboratory onto the surface inside Gale Crater on range of possible dates was scheduling the landing to
Mars and use it to investigate the area’s past and pres- occur when NASA orbiters at Mars are passing over the
ent environments. The landing will use active guidance landing site. Such scheduling aims to allow the orbiters
for improved landing accuracy and a sky crane maneu- to receive radio transmissions from the Mars Science
ver for the final descent to the surface. The mission’s Laboratory spacecraft during its descent through the
mobile laboratory is the Curiosity rover, equipped with atmosphere and landing. If the landing is not successful,
10 science investigations and a robotic arm that can drill this strategy will provide more information than would be
into rocks, scoop up soil and deliver samples to internal possible with the alternative of relying on transmissions
analytical instruments. The mission will assess whether from the Mars Science Laboratory directly to Earth.
the area has offered conditions favorable for life and Landing on Mars is always difficult, with success uncer-
whether conditions were favorable for preserving a tain. After an unsuccessful attempted Mars landing by
rock record of evidence about whether life has existed Mars Polar Lander in 1999 without definitive information
there. The Curiosity rover has the capability to drive for on the cause of the mishap, NASA set a high priority on
12.4 miles (20 kilometers) or more during a mission last- communication during subsequent Mars landings.
ing one Martian year (98 weeks).
Interplanetary Cruise and Approach to Mars
Launch
The Mars Science Laboratory spacecraft is flying for
A two-stage Atlas V 541 launch vehicle lofted the Mars 254 days to get from Earth to Mars. Most of this period
Science Laboratory spacecraft from Launch Complex is the cruise phase of the mission. The final 45 days are
41 at Cape Canaveral Air Force Station, Fla. at 10:02 the approach phase.
EST on Nov. 26, 2011. The rocket was produced by
United Launch Alliance, a joint venture of Boeing Co. Cruise Phase
and Lockheed Martin Corp. The three numbers in the
541 designation signify a payload fairing, or nose cone, Key activities during cruise included checkouts of the
approximately 5 meters (16.4 feet) in diameter; four spacecraft and its science instruments, tracking of
solid-rocket boosters fastened alongside the central the spacecraft, attitude adjustments for changes in
common core booster; and a one-engine Centaur up- pointing of the solar array and antennas, and planning
per stage. The launch was on the second day into a and execution of maneuvers to adjust its trajectory.
launch period that went from Nov. 25 through Dec.18. It Opportunities for additional trajectory correction ma-
was moved from Nov. 25 to allow time for removal and neuvers, if needed, are scheduled during the approach
replacement of a flight-termination system battery. phase.

The launch successfully put the Mars Science Labora- During cruise and approach phases, the spacecraft is
tory mission on its way toward Mars. spin-stabilized at about two rotations per minute. The
attitude of the spacecraft’s axis of rotation relative to
Curiosity’s Launch Period Earth and the sun affects telecommunications, power
and thermal performance. The plane of the solar array
As Earth and Mars race around the sun, with Earth on the cruise stage is perpendicular to that axis, and the
on the inside track, Earth laps Mars about once every two antennas used during cruise are pointed in line with
26 months. Launch opportunities to Mars occur at the that axis, in the direction the array faces. The parachute
same frequency, when the planets are configured so low-gain antenna, used during the first two months of
that a spacecraft launched from Earth will move out- the trip when the angle between the sun and Earth was
ward and intersect with Mars in its orbit several months relatively large, works at a wider range of pointing angles
later. This planetary clockwork, plus the launch vehicle’s than possible with the medium-gain antenna, which is
power, the spacecraft’s mass, and the desired geometry mounted on the cruise stage.
and timing for the landing on Mars were all factors in
determining the range of possible launch dates.

Mars Science Laboratory Landing 25 Press Kit
Thrusters on the cruise stage are fired to adjust the It removed most of the intentional offset, putting the
spacecraft’s flight path during trajectory correction ma- spacecraft on a course missing the target point in space
neuvers. The first two trajectory corrections, on Jan. 11 and time by about 3,000 miles (5,000 kilometers) and
and March 26, removed most of the launch-day trajec- 20 minutes. The March 26 maneuver used about nine
tory’s intentional offset. That intentional offset away from minutes of thruster firings to achieve a velocity change
Mars was a precaution to avoid the possibility of hitting of 2 miles per hour (0.9 meters per second). It put the
Mars with the launch vehicle’s upper stage. Prior to the spacecraft on a Mars-intersect course for the first time.
first maneuver, the Mars Science Laboratory spacecraft
was on a course that would have missed Mars by about For the mission’s third scheduled opportunity for a
25,000 miles (about 40,000 kilometers) and sped past trajectory correction, on June 26, the navigation team
the planet about 14 hours later than the targeted arrival designed a maneuver to put the spacecraft on course
time. to reach the top of Mars’ atmosphere at the right place,
right angle and right time. This third trajectory correction
The Jan. 11 trajectory correction used about 59 minutes used 40 seconds of thruster firings to adjust the location
of thruster firings, changing the velocity of the spacecraft where the spacecraft will enter Mars’ atmosphere by
by about 12.3 miles per hour (5.5 meters per second). about 125 miles (about 200 kilometers) and to advance
the time of entry by about 70 seconds.

Schematic view of Mars Science Laboratory cruise phase Six trajectory correction maneuvers (TCMs) are scheduled
from Earth to Mars. Dates are given in Universal Time. during the voyage from Earth to Mars. Arrival at Mars will be
Aug. 6, 2012, Universal Time.

The final 45 days leading up to the Mars landing are the The intense period called the entry, descent and landing
approach phase. This phase includes opportunities for (EDL) phase of the mission begins when the spacecraft
up to three additional trajectory correction maneuvers. reaches the top of the Martian atmosphere, traveling at
These remaining opportunities are on July 29, Aug. 4 about 13,200 miles per hour (5,900 meters per sec-
and Aug. 5, Universal Time (July 28, Aug 3 and Aug. 5, ond). EDL ends about seven minutes later with the rover
Pacific Time), with an additional make-up time available stationary on the surface. From just before jettison of
for the Aug. 4 maneuver if that opportunity is not used. the cruise stage, 10 minutes before entry, to the cutting
Factors that could lead to the need for final-week cor- of the sky crane bridle, the spacecraft goes through six
rection of trajectory predictions include calculations of different vehicle configurations and fires 76 pyrotechnic
the effects of solar-radiation pressure and the effects of devices, such as releases for parts to be separated or
thruster firings used to keep spacecraft antennas point- deployed.
ed toward Earth.
The top of Mars’ atmosphere is a gradual transition to
Trajectory correction maneuvers combine assessments interplanetary space, not a sharp boundary. The at-
of the spacecraft’s trajectory with calculations of how to mospheric entry interface point — the navigators’ aim
use the eight thrusters on the cruise stage to alter the point during the flight to Mars — is set at 2,188.6 miles
trajectory. Navigators’ assessments of the spacecraft’s (3,522.2 kilometers) from the center of Mars. That alti-
trajectory use three types of tracking information from tude is 81.46 miles (131.1 kilometers) above the ground
ground antennas of NASA’s Deep Space Network in elevation of the landing site at Gale Crater, though the
California, Spain and Australia. One method is ranging, entry point is not directly above the landing site. While
which measures the distance to the spacecraft by timing descending from that altitude to the surface, the space-
precisely how long it takes for a radio signal to travel to craft will also be traveling eastward relative to the Mars
the spacecraft and back. A second is Doppler, which surface, covering a ground-track distance of about
measures the spacecraft’s speed relative to Earth by 390 miles (about 630 kilometers) between the atmo-
the amount of shift in the pitch of a radio signal from the spheric entry point and the touchdown target.
craft. A newer method, called delta differential one-way
range measurement, adds information about the location Ten minutes before the spacecraft enters the atmo-
of the spacecraft in directions perpendicular to the line sphere, it sheds the cruise stage. The Mars Science
of sight. For this method, pairs of antennas on differ- Laboratory Entry, Descent and Landing Instrument
ent continents simultaneously receive signals from the (MEDLI) Suite begins taking measurements. The data
spacecraft, and then the same antennas observe natural MEDLI provides about the atmosphere and about the
radio waves from a known celestial reference point, such heat shield’s performance will aid in design of future
as a quasar, which serves as a navigation reference Mars landings.
point.
A minute after cruise stage separation, nine minutes
Some activities during the final five days of the approach before entry, small thrusters on the back shell halt the
phase will prepare the spacecraft for its atmospheric two-rotation-per-minute spin that the spacecraft main-
entry, descent and landing. These activities include pre- tained during cruise and approach phases. Then, the
heating of some components and enabling others. The same thrusters on the back shell orient the spacecraft
schedule includes four opportunities to update param- so the heat shield faces forward, a maneuver called
eters for the autonomous software controlling events “turn to entry.”
during the entry, descent and landing. Some parameters
give the spacecraft’s onboard computer knowledge After the turn to entry, the back shell jettisons two solid-
about where the vehicle is relative to Mars. Other param- tungsten weights, called the “cruise balance mass de-
eters may be updated based on observations by Mars vices.” Ejecting these devices, which weigh about 165
Reconnaissance Orbiter of the Red Planet’s variable at- pounds (75 kilograms) each, shifts the center of mass of
mospheric conditions in the week before landing. These the spacecraft. During the cruise and approach phases,
updates can fine-tune the spacecraft’s autonomous the center of mass is on the axis of the spacecraft’s
controls for its descent through the atmosphere. stabilizing spin. Offsetting the center of mass for the pe-
riod during which the spacecraft experiences dynamic

Mars Science Laboratory Landing 27 Press Kit
pressure from interaction with the atmosphere gives the spacecraft is at an altitude of about 5 miles (about
the Mars Science Laboratory the ability to generate lift, 8 kilometers) and traveling at a velocity of about 280
essentially allowing it to fly through the atmosphere. The miles per hour (125 meters per second).
ability to generate lift during entry increases this mis-
sion’s capability to land a heavier robot, compared to As the heat shield separates, the Mars Descent Imager
previous Mars surface missions. begins recording video, looking in the direction the
spacecraft is flying. The imager records continuously
The spacecraft also manipulates that lift, using a tech- from then through the landing. The rover, with its
nique called “guided entry,” to steer out unpredictable descent-stage “rocket backpack,” is still attached to
variations in the density of the Mars atmosphere, im- the back shell on the parachute. The terminal descent
proving the precision of landing on target. sensor, a radar system mounted on the descent stage,
begins collecting data about velocity and altitude.
During guided entry, small thrusters on the back shell
can adjust the angle and direction of lift, enabling the The back shell, with parachute attached, separates
spacecraft to control how far downrange it is flying. The from the descent stage and rover about 85 seconds
spacecraft also performs “S” turns, called bank rever- after heat shield separation. At this point, the space-
sals, to control how far to the left or right of the target craft is about 1 mile (1.6 kilometers) above the ground
it is flying. These maneuvers allow the spacecraft to and rushing toward it at about 180 miles per hour
correct position errors that may be caused by atmo- (about 80 meters per second). All eight throttleable
sphere effects, such as wind, or by spacecraft modeling retrorockets on the descent stage, called Mars landing
errors. These guided entry maneuvers are performed engines, begin firing for the powered descent phase.
autonomously, controlled by the spacecraft’s computer
in response to information that a gyroscope-containing After the engines have decelerated the descent to
inertial measurement unit provides about deceleration about 1.7 miles per hour (0.75 meters per second), the
and direction, indirect indicators of atmospheric density descent stage maintains that velocity until rover touch-
and winds. down. Four of the eight engines shut off just before
nylon cords begin to spool out to lower the rover from
During EDL, more than nine-tenths of the decelera- the descent stage in the “sky crane” maneuver. The
tion before landing results from friction with the Mars rover separates its hard attachment to the descent
atmosphere before the parachute opens. Peak heating stage, though still attached by the sky crane bridle and
occurs about 75 seconds after atmospheric entry, when a data “umbilical cord,” at an altitude of about 66 feet
the temperature at the external surface of the heat shield (about 20 meters), with about 12 seconds to go before
will reach about 3,800 degrees Fahrenheit (about 2,100 touchdown.
degrees Celsius). Peak deceleration occurs about
10 seconds later. Deceleration could reach 15 g, but The rover’s wheels and suspension system, which
a peak in the range of 10 g to 11 g is more likely. double as the landing gear, pop into place just be-
fore touchdown. The bridle is fully spooled out as the
After the spacecraft finishes its guided entry maneuvers, spacecraft continues to descend, so touchdown oc-
a few seconds before the parachute is deployed, the curs at the descent speed of about 1.7 miles per hour
back shell jettisons another set of tungsten weights (0.75 meters per second). When the spacecraft senses
to shift the center of mass back to the axis of symmetry. touchdown, the connecting cords are severed and
This set of six weights, the “entry balance mass the descent stage flies out of the way, coming to the
devices,” each has a mass of about 55 pounds surface at least 492 feet (150 meters) from the rover’s
(25 kilograms). Shedding them re-balances the position, probably more than double that distance.
spacecraft for the parachute portion of the descent.
Soon after landing, the rover’s computer switches from
The parachute, which is 51 feet (almost 16 meters) in entry, descent and landing mode to surface mode.
diameter, deploys about 254 seconds after entry, at an This initiates autonomous activities for the first Martian
altitude of about 7 miles (11 kilometers) and a velocity of day on the surface of Mars, Sol 0. The time of day at
about 900 miles per hour (about 405 meters per sec- the landing site is mid afternoon — about 3 p.m. local
ond). About 24 more seconds after parachute deploy- mean solar time at Gale Crater.
ment, the heat shield separates and drops away when

Profile of entry, descent and landing events, for one typical case. Exact timing will be determined by atmospheric conditions on
landing day.

Timing Uncertainties During Entry, Descent and 55 seconds or as long as about 170 seconds. Times
Landing given in the above description and on the accompany-
ing graphic are for a typical case, with touchdown
The span of time from atmospheric entry until touch- 416 seconds after entry.
down is not predetermined. The exact timing and
altitude for key events depends on unpredictable factors Mars Surface Operations
in atmospheric conditions on landing day. The guided
entry technique enables the spacecraft to respond The planned operational life for the Mars Science
and adapt to the atmospheric conditions it encounters Laboratory is one Martian year on the surface. One
more effectively than any previous Mars mission. The Martian year is 687 Earth days, or 669 Martian days,
span between the moment the spacecraft passes the which are called sols. Each sol is 24 hours, 39 minutes,
entry interface point and a successful touchdown in the 35.244 seconds long. The landing site is in an equato-
target area of Gale Crater could be as short as about rial region, at 4.5 degrees south latitude. The season in
380 seconds or as long as about 460 seconds. Times Mars’ southern hemisphere at the beginning and end of
for the opening of the parachute could vary by 10 to the prime mission is late winter, about two thirds of the
20 seconds for a successful landing. The largest vari- way from winter solstice to spring equinox.
able during EDL is the length of time the spacecraft
spends on the opened parachute. Curiosity could be One Martian year is how long the scientists and en-
hanging below a fully inflated chute as briefly as about gineers operating the rover will have to achieve the

Mars Science Laboratory Landing 29 Press Kit
mission’s science goals. Adding to the challenge, some as Sol 1. On Curiosity’s Sol 0, if the landing has been
periods of the mission will not be fully available for sci- successful, the rover will check its health and measure
ence tasks. These include an initial health checkout for its tilt. It will fire all of its pyrotechnic devices for releas-
about 10 sols or more after landing and about 20 sols ing post-landing deployments. Spring-loaded deploy-
in April 2013 when communications will be restricted ments, such as removal of dust covers from the Hazard-
due to Mars’ position nearly behind the sun from Earth. Avoidance cameras (Hazcams), occur immediately
Strategies for maximizing the science accomplishments when pyros are fired. Motor-driven deployments, such
in the time available include extensive preparations as raising the high-gain antenna dish and raising the
before landing, efficiently coordinated use of the rover’s camera mast, are scheduled for later sols.
capabilities and flexibility for responding to discoveries.
Curiosity is also programmed to take images with its
The structure of science activities is based on sending front and rear Hazcams on Sol 0 both before and after
a set of commands to the rover each Martian morning removal of the dust covers. It is possible but unlikely that
for the activities to be performed during that sol. The these images will reach Earth via orbiter relay on landing
activity plan for a sol needs to fit within the constraints night. The low volume of data that will fit into early relays
of time, power and spacecraft-temperature factors, and makes about 15 hours after landing a more likely time
data downlink volume for that sol. During a communica- for Earth to receive these first images from Curiosity’s
tion relay opportunity when an orbiter passes overhead landing site. The first look at some color images taken
in the Martian midafternoon, the rover transmits data just before landing by the Mars Descent Imager may
about the sol’s activities. Any of the sol’s results that will come at about the same time. These may allow a deter-
influence the next sol’s planning need to be included in mination of the rover’s precise location.
this downlink, though additional data from the sol can
be transmitted during later relay opportunities. A commissioning phase during the first several weeks
of Mars surface operations prescribes steps to reach
With data from preceding sols, the rover team needs full-pace science operations safely. This phase will begin
to make decisions for each sol, such as what targets with about a month of characterization activities to learn
to approach, what instruments to use, what observa- how all the subsystems and instruments on the Curiosity
tions to make and what downlink priority level to assign rover are functioning after landing and within the environ-
for each set of data generated during the sol or stored ment and gravitational field of Mars.
onboard from earlier sols. The rover team’s engineers
collaborate with scientists to determine what activities The first drive will probably take place more than a week
are safe and feasible, and to develop and check the after landing. First movements of the robotic arm and
sequences of commands for transmission to the rover. sampling tools are scheduled to be part of the char-
acterization activities following the first drive. Following
For the first three months of Mars surface operations, the characterization activities, special precautions will
the team will work on a Mars time schedule to make continue to apply for each first-time activity. Collection of
best use of the key hours between when one sol’s science data by some instruments is scheduled to begin
downlink is received and when the next sol’s commands on Sol 1, and science activities will ramp up during the
must be ready, whatever time of day that is at the commissioning phase. For example, an analysis of the
operations center at NASA’s Jet Propulsion Laboratory, composition of Mars’ atmosphere is a scientific priority
Pasadena, Calif. Team members’ work shift will begin for early in the mission.
about 40 minutes later each day than on the preceding
day because a Martian sol is that much longer than an Priority activities for Sol 1 will not require commands
Earth day. After these three months, operations will tran- from Earth. They are built into command sequences
sition to an Earth-day work schedule and will become stored onboard from before landing. One priority is to
more geographically distributed as non-Pasadena team test motions of the rover’s high-gain antenna for direct
members return to their home institutions and partici- communications with Earth. Use of this antenna will be
pate through teleconferencing. the standard mode for sending commands from Earth
to Curiosity. The Sol 1 plan includes using the Mars
The landing sol is designated as Sol 0, a change from Hand Lens Imager (MAHLI) to take the first post-landing
the practice of the Mars Exploration Rover missions, color image. MAHLI is on the robotic arm, which will
which designated landing sols of Spirit and Opportunity be in its stowed position, with MAHLI looking off to the

Mars Science Laboratory Landing 30 Press Kit
side of the rover, so what scene appears in the first trol hub at NASA’s Jet Propulsion Laboratory, Pasadena,
color image taken from Gale Crater will be determined Calif.
by the orientation of the rover when it touches down.
The Rover Environmental Monitoring Station and the As the spacecraft travels from Earth to Mars during the
Radiation Assessment Detector are also in the Sol 1 cruise and approach phases of the mission, it commu-
plan for collecting data about environmental conditions nicates directly with Earth in the X-band portion of the
at the landing site. Weather information and the image radio spectrum (at 7 to 8 gigahertz). For this, the space-
from MAHLI may be received on Earth the second day craft uses a transponder and amplifier in the spacecraft’s
after landing. descent stage and two antennas. One of the antennas,
the parachute low-gain antenna, is on the aeroshell’s
On Sol 2, if all is proceeding well, Curiosity will raise the parachute cone, which is exposed through the center of
mast holding the Mast Camera (Mastcam), Chemistry the cruise stage. The other, the medium-gain antenna,
and Camera (ChemCam), and Navigation Camera is mounted on the cruise stage. The parachute low-
(Navcam). This is a priority so that Navcam can image gain antenna provided communications during the early
the sky. These early Navcam images will help the rover weeks of the cruise to Mars, and will do so again starting
determine the location of the sun and calculate the angle shortly before cruise-stage separation. For most of the
toward Earth from that knowledge of the sun’s position. voyage, the job switched to the medium-gain antenna,
This calculation will be used for pointing the high-gain which provides higher data rates but requires more re-
antenna toward Earth. Images taken by cameras on the strictive pointing toward Earth. The telecommunications
mast, showing calibration targets and the terrain around system provides position and velocity information for
the rover, may reach Earth during the first few days after navigation, as well carrying data and commands.
landing.
Communication during atmospheric entry, descent and
After completion of the commissioning phase, the pace landing is a high priority. Landings on Mars are notori-
of driving and the frequency of multi-sol stops for acquir- ously difficult. If this landing were not successful, main-
ing and analyzing rock or soil samples will be deter- taining communications during the entry, descent and
mined by team decisions about science priorities. Some landing would provide critical diagnostic information that
possible destinations identified in advance from orbit could influence the design of future missions.
may be within several weeks of driving distance from the
landing site. With the time taken to investigate nearer All three orbiters currently active at Mars — NASA’s
stopping points, other likely destinations might be more Mars Odyssey and Mars Reconnaissance Orbiter and
than a year away. the European Space Agency’s Mars Express — will be
at positions where they can receive transmissions from
Communications Strategy the Mars Science Laboratory spacecraft during its entry,
descent and landing. These transmissions to the orbit-
Like all of NASA’s interplanetary missions, the Mars ers use the ultra-high frequency (UHF) portion of the
Science Laboratory will rely on the agency’s Deep radio spectrum (at about 400 megahertz) from three
Space Network to communicate with the spacecraft different UHF antennas. The parachute UHF antenna,
and to track it during flight. The network has groups of mounted on the back shell, transmits information from
antennas at three locations: at Goldstone in California’s a few minutes before atmospheric entry until the rover
Mojave Desert; near Madrid, Spain; and near Canberra, and descent stage separate from the back shell. At that
Australia. These locations are about one-third of the point, the descent UHF antenna on the descent stage
way around the world from each other. That assures, takes over. When the rover drops away from the descent
whatever time of day it is on Earth, at least one of them stage on its sky-crane bridle, the rover UHF antenna is
will have the spacecraft in view during its trip from Earth exposed to begin transmissions that continue through
through landing. At least one location will have Mars in landing.
view at any time during the rover’s Mars-surface opera-
tions. Each complex is equipped with one antenna The orbiters relay to Earth via X-band the information
230 feet (70 meters) in diameter, at least two antennas they receive from the Mars Science Laboratory during
112 feet (34 meters) in diameter, and smaller antennas. this critical period. Only Odyssey relays the information
All three complexes communicate directly with the con- immediately, however. The other two orbiters record

Mars Science Laboratory Landing 31 Press Kit
data from the Mars Science Laboratory spacecraft, hold reaching Earth with confirmation of the first events of that
it onboard, and send it to Earth hours later. process, Curiosity will actually be on the surface of Mars
already, whether the landing was successful or not.
The Odyssey relay, called “bent pipe,” is what the flight
team and the public will rely upon on landing day for The communication links are not necessary for a suc-
step-by-step information about the latter part of the cessful landing. Under some scenarios of communica-
descent and landing. Odyssey will not begin receiving tion difficulties, the flight team on Earth could have
transmissions from Mars Science Laboratory until about no confirmation of safe landing for a day or more
two minutes after atmospheric entry. After first acquisi- and still recover a successful mission after regaining
tion of signal, the orbiter may lose and regain the signal communication.
more than once as the descending spacecraft goes
through changes in configuration. Odyssey will be in During Mars surface operations, the rover Curiosity has
position to continue receiving and relaying information multiple options available for receiving commands from
from Curiosity for about half a minute to more than two mission controllers on Earth and for returning rover sci-
minutes after the rover lands. Then the orbiter will drop ence and engineering information.
below the horizon from the landing-site perspective.
Mission engineers are uncertain how soon after landing Curiosity has the capability to communicate directly with
the signal will be lost, because of uncertainty in dura- Earth via X-band links with the Deep Space Network.
tion of the entry, descent and landing process, and the This capability will be used routinely to deliver com-
possibility that Curiosity could land where a hill or other mands to the rover each morning on Mars. It can also
obstruction blocks the line of sight between the rover be used to return information to Earth, but only at
and the orbiter. relatively low data rates — on the order of kilobits per
second — due to the rover’s limited power and antenna
The Mars Science Laboratory spacecraft will also size, and to the long distance between Earth and Mars.
transmit in X-band during its entry, descent and land-
ing process. This is the expected path for confirma- Curiosity will return most information via UHF relay links,
tion of the initial events in the process. Due to signal using one of its two redundant Electra-Lite radios to
strength constraints, these transmissions will be simple communicate with a Mars orbiter passing overhead. In
tones, comparable to semaphore codes, rather than full their trajectories around Mars, the Mars Reconnaissance
telemetry. The Deep Space Network will listen for these Orbiter and Mars Odyssey orbiter each fly over the
direct-to-Earth transmissions. However, Earth will go out Curiosity landing site at least once each afternoon and
of view of the spacecraft, “setting” below the Martian once each morning before dawn. While these contact
horizon, partway through the descent, so the X-band opportunities are short in duration, typically lasting only
tones will not be available for confirming the final steps about 10 minutes, the proximity of the orbiters allows
in descent and landing. The X-band antenna in use Curiosity to transmit at much higher data rates than the
from cruise-stage separation until atmospheric entry is rover can use for direct-to-Earth transmissions. The rov-
the parachute low-gain antenna located on the back er can transmit to Odyssey at up to about 0.25 megabit
shell. Then, transmissions are shifted to a tilted low-gain per second and to the Mars Reconnaissance Orbiter at
antenna, also on the back shell. This tilted antenna will up to about 2 megabits per second. The orbiters, with
transmit tones during the banking maneuvers of the their higher-power transmitters and larger antennas, then
guided entry. About five minutes after the spacecraft en- take the job of relaying the information via X-band to the
ters the atmosphere, possibly shortly after the parachute Deep Space Network on Earth. Mission plans call for
opens, Earth will set, ending receipt of X-band tones. By the return of 250 megabits of Curiosity data per Martian
then, the bent-pipe relay via Odyssey may have begun. day over these relay links. The links can also be used for
delivering commands from Earth to Curiosity.
Radio transmissions travel at the speed of light. The
distance between Mars and Earth on Curiosity’s landing While not planned for routine operational use dur-
day, 154 million miles (248 million kilometers), means the ing Curiosity’s surface mission, the European Space
signal takes 13.8 minutes to cross at light speed. The Agency’s Mars Express orbiter will be available as a
whole process of entry, descent and landing takes about backup communications relay asset should NASA’s relay
seven minutes. By the time any transmissions could be orbiters become unavailable for any period of time.

Mars Science Laboratory Landing 32 Press Kit
Planetary Protection with alcohol and other solvents. Components tolerant of
high temperature were heated to reduce spore burden
When sending missions to Mars, precautions must be according to NASA specification, at temperatures rang-
taken to avoid introduction of microbes from Earth by ing from 230 to 295 degrees Fahrenheit (110 to 146
robotic spacecraft. This is consistent with United States degrees Celsius) for durations up to 144 hours. The
obligations under the 1967 Outer Space Treaty, the planetary protection team carefully sampled the surfac-
international treaty stipulating that exploration must be es and performed microbiological tests to demonstrate
conducted in a manner that avoids harmful contami- that the spacecraft meets requirements for biological
nation of celestial bodies. “Planetary protection” is the cleanliness.
discipline responsible for the development of rules and
practices used to avoid biological contamination in the The Mars Science Laboratory is also complying with a
process of exploration. NASA has a planetary protection requirement to avoid going to any site on Mars known
officer responsible for establishing and enforcing plan- to have water or water-ice within 3.3 feet (1 meter) of
etary protection regulations. Each spacecraft mission is the surface. This is a precaution against any landing-day
responsible for implementing measures to comply with accident that could introduce hardware not fully steril-
the regulations. In compliance with the treaty and NASA ized by dry heat into an environment where heat from
regulations, the Mars Science Laboratory flight hardware the mission’s radioisotope thermoelectric generator and
has been designed and built to meet planetary protec- a Martian water source could provide conditions favor-
tion requirements. able for microbes from Earth to grow on Mars.

NASA’s primary strategy for preventing contamina- Another way of making sure the mission does not trans-
tion of Mars with Earth organisms is to be sure that all port Earth life to Mars is to ensure that any hardware not
hardware going to the planet is biologically clean. The meeting cleanliness standards does not go to Mars ac-
Mars Science Laboratory mission is allowed to carry up cidentally. When the Atlas launch vehicle’s upper stage
to 500,000 bacterial spores on the entire flight system. Centaur separated from the spacecraft, the two objects
That’s about one tenth as many as in a typical teaspoon were traveling on nearly identical trajectories. To prevent
of seawater. Spore-forming bacteria have been the the possibility of the Centaur hitting Mars, that shared
focus of planetary protection standards because these flight path was deliberately set so that the spacecraft
bacteria can survive harsh conditions for many years as would miss Mars if not for later maneuvers to adjust its
inactive spores. One requirement for this mission is that trajectory. By design, the Centaur was never aimed at
the exposed interior and exterior surfaces of the landed Mars.
system, which includes the rover, parachute and back
shell, must not carry a total number of bacterial spores Portions of the flight hardware will impact the surface of
greater than 300,000, with the average spore density Mars as part of a normal landing event. This impact may
not exceeding 300 spores per square meter (about 11 cause the hardware to split open and potentially release
square feet). This ensures that the biological load is not spores trapped inside the hardware during manufactur-
concentrated in one place. The heat shield and descent ing processes. To ensure MSL does not exceed the
stage will hit the ground hard enough that hardware spore allocation, studies were conducted on various
could break open. The number of spores inside this materials, including paint, propellants and adhesives, to
hardware that could be exposed by the hard landings determine the number of spores in a given volume. In
of these components must be included in the 500,000 many cases the parts of the spacecraft containing these
maximum number. materials were treated with dry heat microbial reduction
to reduce the number of spores. For hardware expect-
Two common methods used for reducing the number ed to impact Mars, such as the cruise stage after its
of spores on the spacecraft are alcohol wipe clean- separation from the aeroshell, a detailed thermal analy-
ing and dry heat microbial reduction. Technicians and sis was conducted to make sure that plunging through
engineers who assembled the spacecraft and prepared Mars’ atmosphere creates enough heat that few to no
it for launch routinely cleaned surfaces by wiping them spores survive.

Mars Science Laboratory Landing 34 Press Kit
Spacecraft
The Mars Science Laboratory spacecraft consists of two separation events, the cruise stage performs es-
four major elements: rover, descent stage, aeroshell sential tasks of the flight, though it uses the computer
and cruise stage. The rover, Curiosity, has the science inside the rover.
payload and systems that enable the rover to use the
payload effectively and send home the results. The The cruise stage primary structure is aluminum. An in-
descent stage performs the final moments of delivering ner ring connects to the launch vehicle interface and the
the rover to the surface of Mars. The aeroshell, which back shell interface plate. A series of ribs connect other
includes the heat shield and the back shell, provides components. The cruise propulsion system is used to
thermal protection and maneuverable lift during the initial maintain the spacecraft’s spin rate, adjust the space-
portion of descent through the Martian atmosphere, and craft’s orientation, and provide propulsion for trajectory
then a parachute ride for the next portion of the descent. correction maneuvers during the trip between Earth
The cruise stage provides trajectory maneuvers, electri- and Mars. Two clusters of thrusters each include four
cal power, communications and other functions during thruster engines in different orientations enabling differ-
the eight months from launch to landing. ent directions of thrust. Each of the eight thrusters can
provide about 1.1 pounds (5 newtons) of force. They
Cruise Stage use hydrazine, a monopropellant that does not re-
quire an oxygen source. Hydrazine is a corrosive liquid
The cruise stage is doughnut-shaped, about five times compound of nitrogen and hydrogen that decomposes
wider than it is tall, with 10 radiators arranged around explosively into expanding gases when exposed to a
the perimeter. The hole of the doughnut sits over a catalyst in the thrusters. Two spherical propellant tanks
cone holding the parachute on top of the aeroshell. One on the cruise stage, each 19 inches (48 centimeters) in
surface of the cruise stage was attached to the launch diameter, supply the pressurized propellant. Aerojet built
vehicle. That attachment was severed within the first the thrusters at its Redmond, Wash., facility. On both
hour after launch. The other surface of the cruise stage the cruise stage and descent stage, fuel tanks are from
attaches to the top of the aeroshell. That attachment ATK Space Systems, Inc., Commerce, Calif.; and pres-
will be severed 10 minutes before the spacecraft enters surant tanks are from Arde, Inc., Carlstadt, N.J.
Mars’ atmosphere. During the 254 days between those

Cruise Stage

Back Shell
Interface Plate
Parachute Support
Structure
Back Shell
Parachute

Descent Stage Entry
Vehicle
Bridle System
Umbilical
Device

Rover

Heat Shield

Mars Science Laboratory flight system, expanded view

Mars Science Laboratory Landing 35 Press Kit
The spacecraft spins at about two rotations per minute friction with Mars’ atmosphere and provides other
for stability on its way to Mars. The cruise stage moni- functions.
tors the spin rate and the spacecraft’s attitude (orienta-
tion) with a star scanner and one of two sun sensor The Mars Science Laboratory aeroshell is not only the
assemblies. Each of the sun sensor assemblies, from biggest ever built for a planetary mission, but also incor-
Adcole Corp., Marlborough, Mass., includes four sun- porates major innovations in attitude control for guided
sensor heads pointing in different directions. Based on entry and in thermal protection material. Lockheed
star tracking and sun sensing information, the cruise Martin Space Systems, Denver, built the aeroshell’s heat
stage uses its thrusters as necessary to maintain the shield and back shell.
spin rate and attitude.
The diameter of the heat shield is 14.8 feet (4.5 meters).
Most of the electrical power for the spacecraft during the For comparison, heat shields of the Apollo capsules
trip from Earth to Mars is provided by sunshine hitting that returned astronauts to Earth after visits to the moon
a ring-shaped array of photovoltaic cells on the upper were just under 13 feet (4 meters) in diameter, and the
surface of the cruise stage. The multi-mission radioiso- heat shields for the Mars Exploration Rovers, Spirit and
tope thermoelectric generator on the rover supplements Opportunity, were 8.7 feet (2.65 meters).
the electricity provided by the cruise solar array on the
way to Mars. The solar array has six physical panels This aeroshell, unlike any predecessor for an extrater-
totaling 138 square feet (12.8 square meters) of active restrial mission, has a steering capability. This is a key
photovoltaic area. The photovoltaic cells from Emcore to the mission’s guided entry innovation for added
Corp., Albuquerque, N.M., use layers of three different precision in landing. During a crucial portion of descent
materials to gain electricity from different portions of the through the upper atmosphere of Mars, before the back
solar spectrum. The layers are gallium indium phospho- shell deploys its parachute, the center of mass of the
rus, gallium arsenide and germanium. If operated at full spacecraft will be offset from the axis of symmetry (a
capacity at Earth, the array could produce about 2,500 line through the center of the aeroshell). This offset puts
watts, which would exceed the spacecraft’s needs. the aeroshell at an angle to its direction of movement,
The array and its operation are designed to satisfy the creating lift as the spacecraft interacts with the atmo-
mission’s requirements from launch day to the Mars ap- sphere. With lift, the spacecraft can fly like a wing, rather
proach. At its farthest from the sun, during the approach than dropping like a rock. A reaction control system with
to Mars, the array will produce 1,080 watts or more, small thrusters to adjust the orientation of the spacecraft
even when facing as much as 43 degrees away from can steer banking turns. A series of turns can shorten
the sun. the net horizontal distance the spacecraft covers during
its descent. Performed in response to sensing how the
Another important function for the cruise stage is to spacecraft is reacting to unpredictable variability in the
maintain temperatures within designed ranges for the atmosphere, the maneuvers counteract the unpredict-
parts of the spacecraft inside the aeroshell as well as ability and provide a more precise landing.
for the cruise stage itself. The 10 radiators of the heat-
rejection system are mounted as a ring around the The heat shield uses a different thermal protection
outer edge of the cruise stage. Fluid pumped through a system than used on earlier Mars missions’ heat
circulatory system disperses heat from the rover’s multi- shields, because the unique entry trajectory profile and
mission radioisotope thermoelectric generator to warm the mass and size of the vehicle could create external
the electronics of the cruise stage and to be released temperatures up to 3,800 degrees Fahrenheit (about
into space by the radiators. 2,100 degrees Celsius). The heat shield is covered with
tiles of phenolic impregnated carbon ablator (PICA)
The medium-gain antenna mounted on the cruise stage material. NASA Ames Research Center, Moffett Field,
serves in telecommunications with Earth during most of Calif., invented the PICA material; Fiber Materials Inc.,
the trip from Earth to Mars. Biddeford, Maine, made the tiles. PICA was first flown
as the thermal protection system on the heat shield of
Aeroshell NASA’s Stardust Sample Return Capsule.

The aeroshell that encapsulates the rover and descent The heat shield carries sensors for collecting data about
stage during the flight to Mars protects them from Mars’ atmosphere and the performance of the heat

Mars Science Laboratory Landing 36 Press Kit
shield. These are part of the Mars Science Laboratory were built by Aerojet, in Richmond, Wash., with throttle
Entry, Descent and Landing Instrument (MEDLI) Suite, valve assemblies from Moog Inc., East Aurora, N.Y. Each
which is described in the Mars Science Laboratory can provide an adjustable amount of thrust up to about
Investigations section of this document. 742 pounds (3,300 newtons). The propulsion system
of the descent stage uses pressurized propellant. Three
The back shell, besides making up the upper portion of spherical fuel tanks provide a usable propellant load of
the capsule protecting the rover during passage through about 853 pounds (about 387 kilograms) of hydrazine,
Mars’ atmosphere, includes several devices used during a propellant that does not require an oxygen source.
the spacecraft’s atmospheric entry and descent. Two spherical tanks of pressurized helium provide pres-
sure for propellant delivery, moderated by a mechanical
The back shell carries two sets of detachable tungsten regulator.
weights for altering the spacecraft’s center of mass.
While the rover is fastened to the descent stage, the two
Eight small thrusters in the upper half of the back shell components together are called the powered descent
are used for the guided entry maneuvers. vehicle. The fastenings are pyrotechnic bolts. Firing to
release these connections commences the spacecraft’s
A conical structure at the top of the back shell holds sky crane maneuver.
the parachute and its deployment mechanism. The
parachute is the largest ever built for an extraterrestrial To perform the sky crane maneuver of lowering the
mission. It uses a configuration called disk-gap-band. It rover on a bridle, the descent stage carries a device
has 80 suspension lines, measures 165 feet (50 meters) called the bridle umbilical and descent rate limiter (BUD).
in length, and opens to a diameter of 51 feet (nearly This cone-shaped device is about 2 feet (two-thirds of
16 meters). Most of the orange and white fabric is nylon, a meter) long. Three tethers of the bridle, attached to
though a small disk of heavier polyester is used near the the rover at three points, are spooled around the BUD,
vent in the apex of the canopy due to higher stresses with enough length to lower the rover about 25 feet (7.5
there. The parachute is designed to survive deployment meters) below the descent stage during the sky crane
at up to Mach 2.2 in the Martian atmosphere and drag maneuver. A slightly longer umbilical, with data and
forces of up to 65,000 pounds. Pioneer Aerospace power connections between the rover and the descent
Corp., South Windsor, Conn., made the parachute. stage, is also spooled around the BUD. A descent brake
in the device governs the rotation rate as the bridle un-
Mounted on the back shell are two antennas — the spools, hence the speed at which gravity pulls the rover
parachute low-gain antenna and the tilted low-gain away from the descent stage. The descent brake, made
antenna — for communicating directly with Earth using by the Starsys division of SpaceDev Inc. (now Sierra
X-band frequencies and another antenna — the para- Nevada Corp.), Poway, Calif., uses gear boxes and
chute UHF antenna — for communicating with Mars banks of mechanical resistors engineered to prevent the
orbiters using an ultra-high frequency (UHF) band. bridle from spooling out too quickly or too slowly. The
cords of the bridle are made of nylon. The BUD also in-
Descent Stage cludes springs for quickly retracting the loose bridle and
umbilical after they are severed at the rover end when
The descent stage of the Mars Science Laboratory does touchdown is detected.
its main work during the final few minutes before touch-
down on Mars. It provides rocket-powered deceleration Through the umbilical, the spacecraft’s main computer
and two bands of telecommunications for a phase of the inside the rover controls activities during the entry,
arrival at Mars after the phases using the heat shield and descent and landing. After the heat shield drops away,
parachute. After reaching a constant vertical velocity, the crucial information for determining the timing of events
descent stage lowers the rover on a bridle and continues comes to that computer from the terminal descent
descent until rover touchdown. sensor, a radar system engineered and built specifically
for this mission. The radar, mounted on the descent
The descent stage uses eight rockets, called Mars land- stage, has six disk-shaped antennas oriented at different
er engines (MLE), positioned around its perimeter in four angles. It measures both vertical and horizontal velocity,
pairs. These are the first throttleable engines for a Mars as well as altitude.
landing since the Mars Viking landings in 1976. They

Mars Science Laboratory Landing 37 Press Kit
The descent stage carries an X-band transponder and Rover Mobility
amplifier and two telecommunication antennas: the de-
scent low-gain antenna for communicating directly with Curiosity’s mobility subsystem is a scaled-up version
Earth via X-band transmissions and the descent UHF of what was used on the three earlier Mars rovers:
antenna for sending information to Mars orbiters. Sojourner, Spirit and Opportunity. Six wheels all have
driver motors. The four corner wheels all have steering
Rover motors. Each front and rear wheel can be independently
steered, allowing the vehicle to turn in place as well as to
The Mars Science Laboratory rover, Curiosity, carries the drive in arcs. The suspension is a rocker-bogie system.
instruments of the mission’s 10 science investigations Combined with a differential connecting the left and right
plus multiple systems that enable the science payload sides of the mobility system, the rocker-bogie design en-
to do its job and send home the results. Key systems ables a six-wheel vehicle to keep all its wheels in contact
include six-wheeled mobility, sample acquisition and with the ground even on uneven terrain, such as with a
handling with a robotic arm, navigation using stereo im- wheel going over a rock as big as the wheel. On each
aging, a radioisotope power source, avionics, software, side, a bogie connects the middle and rear wheels and
telecommunications and thermal control. provides a pivot point between those wheels. The rocker
connects the bogie pivot point to the front wheel. The
The rover’s name was suggested by the winning en- rocker’s pivot point connects to the differential across the
trant in a national naming contest conducted among rover body to the rocker on the other side.
U.S. school students. More than 9,000 students,
ages 5 through 18, submitted entries in late 2008 and Curiosity’s wheels are aluminum, 20 inches (0.5 meter)
early 2009. An essay by Clara Ma of Lenexa, Kans., a in diameter, which is twice the size of the wheels on
12-year-old sixth-grader at the time, was selected by Spirit and Opportunity. They have cleats for traction
NASA in May 2009. and for structural support. Curving titanium spokes
give springy support. The wheels were machined by
Curiosity is 10 feet (3 meters) long (not counting its arm), Tapemation, Scotts Valley, Calif. Titanium tubing for the
9 feet (2.7 meters) wide and 7 feet (2.2 meters) high suspension system came from Litespeed Titanium,
at the top of its mast, with a mass of 1,982 pounds Chattanooga, Tenn.
(899 kilograms), including 165 pounds (75 kilograms) of
science instruments. By comparison, each of the previ- The drive actuators — each combining an electric mo-
ous generation of Mars rovers, Spirit and Opportunity, is tor and gearbox — are geared for torque, not speed.
5.2 feet (1.6 meters) long, 7.5 feet (2.3 meters) wide and Aeroflex Inc., Plainview, N.Y., built the cold-tolerant actua-
4.9 feet (1.5 meters) high, with a mass of 374 pounds tors for the wheels and other moving parts of Curiosity.
(170 kilograms), including about 20 pounds (9 kilograms) The rover has a top speed on flat, hard ground of about
of science instruments. 1.5 inches (4 centimeters) per second. However, under
autonomous control with hazard avoidance, the vehicle
The science payload is described in the Mars Science achieves an average speed of less than half that. The
Laboratory Science Investigations section of this press rover was designed and built to be capable of driving
kit. more than 12 miles (more than 20 kilometers) during the
prime mission. The actual odometry will depend on deci-
Curiosity’s mechanical structure provides the basis for sions the science team makes about allocating time for
integrating all of the other rover subsystems and pay- driving and time for investigating sites along the way.
load instruments. The chassis is the core of the rover.
With insulated surfaces, it forms the shell of the warm For Curiosity, unlike earlier Mars rovers, the mobility
electronics box containing the avionics. The mechani- system doubles as a landing system, directly absorbing
cal subsystem provides deployments that bring the the force of impacting the Martian surface at touchdown.
rover to its full functionality, including deployments of the As on the earlier rovers, the mobility system can also be
remote-sensing mast, robotic arm, antennas and mobil- used for digging beneath the surface by rotating one cor-
ity system. ner wheel while keeping the other five wheels immobile.

Rover Arm and Turret rover body. The diameter of the turret, including the
tools mounted on it, is nearly 2 feet (60 centimeters).
The turret at the end of the Curiosity’s robotic arm holds
two science instruments and three other devices. The The arm has five degrees of freedom of movement
arm places and holds turret-mounted tools on rock and provided by rotary actuators known as the shoulder
soil targets and manipulates the sample-processing azimuth joint, shoulder elevation joint, elbow joint,
mechanisms on the turret. It is strong enough to hold wrist joint and turret joint. The Space Division of MDA
the 73-pound (33-kilogram) turret at full extension of the Information Systems Inc. built the arm in Pasadena,
arm. With the arm extended straight forward, the center Calif.
of the turret is 6.2 feet (1.9 meters) from the front of the

Mars Science Laboratory Landing 39 Press Kit
APXS
Drill CHIMRA

MAHLI

DRT

Turret of tools at the end of Curiosity’s robotic arm

Locations of tools on the turret that is mounted on Curiosity’s Handling for In-Situ Martian Rock Analysis (CHIMRA),
arm are indicated. These include (clockwise from upper which includes a scoop for acquiring soil samples; the Dust
left): the drill for acquiring powdered samples from interiors Removal Tool (DRT) for brushing rock surfaces clean; and the
of rocks; the Alpha Particle X-ray Spectrometer (APXS); Mars Hand Lens Imager (MAHLI).
the sample processing subsystem named Collection and

The science instruments on the arm’s turret are the of the drilled hole is 0.63 inch (1.6 centimeters). The drill
Mars Hand Lens Imager (MAHLI) and the Alpha Particle penetrates the rock and powders the sample to the
X-ray Spectrometer (APXS). The other tools on the tur- appropriate grain size for use in the two analytical instru-
ret are components of the rover’s Sample Acquisition/ ments inside the rover: Sample Analysis at Mars (SAM),
Sample Processing and Handling (SA/SPaH) sub- and Chemistry and Mineralogy (CheMin). The powder
system: the Powder Acquisition Drill System (PADS), travels up an auger in the drill for transfer to sample
the Dust Removal Tool (DRT), and the Collection and processing mechanisms. If the drill bit becomes stuck in
Handling for In-situ Martian Rock Analysis (CHIMRA) a rock, the drill can disengage from that bit and replace
device. it with a spare drill-bit assembly. The arm moves the drill
to engage and capture one of two spare bits in bit boxes
The Powder Acquisition Drill System is a rotary per- mounted to the front of the rover.
cussive drill to acquire samples of rock material for
analysis. It can collect a sample from up to 2 inches The Dust Removal Tool, from Honeybee Robotics, N.Y.,
(5 centimeters) beneath a rock’s surface. The diameter is a metal-bristle brushing device used to remove the

Mars Science Laboratory Landing 40 Press Kit
dust layer from a rock surface or to clean the rover’s of space. In addition, it is a more flexible modular
observation tray. design capable of meeting the needs of a wider variety
of missions as it generates electrical power in smaller
One portion of the Collection and Handling for In-situ increments, slightly more than 110 watts. The design
Martian Rock Analysis device is a motorized, clamshell- goals for the multi-mission radioisotope thermoelectric
shaped scoop, 1.57 inches (4 centimeters) wide, to generator include ensuring a high degree of safety,
collect soil samples from the Martian surface. The other optimizing power levels over a minimum lifetime of
turret-mounted portion of this device has chambers 14 years, and minimizing weight. It is about 25 inches
and labyrinths used for sorting, sieving and portioning (64 centimeters) in diameter by 26 inches (66 centime-
the samples collected by the drill and the scoop. These ters) long and weighs about 99 pounds (45 kilograms).
functions are carried out by manipulating the orienta-
tion of the turret while a vibration device helps move Like previous generations of this type of generator, the
material through the chambers, passages and sieves. multi-mission radioisotope thermoelectric generator is
Samples can be sieved to screen out particles more built with several layers of protective material designed
than 0.04 inch (1 millimeter) across or to screen out to contain its plutonium dioxide fuel in a wide range of
particles more than 0.006 inch (150 microns) across. potential accidents, verified through impact testing. In
The vibration device also aids in creating the appropri- the unlikely event of a launch accident, it is unlikely that
ate portion size and in the delivery action when the any plutonium would have been released or that any-
device drops material into inlet ports of the analytical one would have been exposed to nuclear material. The
instruments. Each of the inlet ports — two for Sample type of plutonium used in a radioisotope power system
Analysis at Mars and one for Chemistry and Mineralogy is different from the material used in weapons and can-
— has a cover that can be opened and closed using a not explode like a bomb. It is manufactured in a ceramic
motor. form that does not become a significant health hazard
unless it becomes broken into very fine pieces or vapor-
An observation tray on the rover allows the Mars Hand ized and then inhaled or swallowed. If there had been
Lens Imager and the Alpha Particle X-ray Spectrometer an accident at the launch of Mars Science Laboratory,
a place to examine collected and processed samples of people who might have been exposed would have
soil and powdered rock. received an average dose of 5 to 10 millirem, equal to
about a week of background radiation. The average
Rover Power American receives 360 millirem of radiation each year
from natural sources, such as radon and cosmic rays.
Rover power is provided by a multi-mission radioisotope
thermoelectric generator (MMRTG) supplied by the U.S. The electrical output from the multi-mission radioiso-
Department of Energy. This generator is essentially a tope thermoelectric generator charges two lithium ion
nuclear battery that reliably converts heat into electric- rechargeable batteries. This enables the power subsys-
ity. It consists of two major elements: a heat source that tem to meet peak power demands of rover activities
contains plutonium-238 dioxide and a set of solid-state when the demand temporarily exceeds the generator’s
thermocouples that convert the plutonium’s heat energy steady output level. The batteries, each with a capac-
to electricity. It contains 10.6 pounds (4.8 kilograms) of ity of about 42 amp-hours, were made by Yardney
plutonium dioxide as the source of the steady supply Technical Products, Pawcatuck, Conn. They are ex-
of heat used to produce the onboard electricity and to pected to go through multiple charge-discharge cycles
warm the rover’s systems during the frigid Martian night. per Martian day.

Radioisotope thermoelectric generators have enabled Rover Telecommunication
NASA to explore the solar system for many years. The
Apollo missions to the moon, the Viking missions to Curiosity has three antennas for telecommunication.
Mars, and the Pioneer, Voyager, Ulysses, Galileo, Cassini Two are for communications directly with NASA’s Deep
and New Horizons missions to the outer solar system all Space Network antennas on Earth using a radio fre-
used radioisotope thermoelectric generators. The multi- quency in the X band (7 to 8 gigahertz). The third is for
mission radioisotope thermoelectric generator is a new communications with Mars orbiters, using the ultra-high
generation designed to operate on planetary bodies with frequency (UHF) band (about 400 megahertz).
an atmosphere, such as Mars, as well as in the vacuum

Mars Science Laboratory Landing 41 Press Kit
X-band communications use a 15-watt, solid-state tive — also serves as the main computer for the rest of
power amplifier fed by the rover’s small deep space the Mars Science Laboratory spacecraft during the flight
transponder, manufactured by General Dynamics from Earth and arrival at Mars. In case the active com-
Advanced Information Systems, Scottsdale, Ariz. Spain puter resets for any reason during the critical minutes
provided the rover’s high-gain antenna, which is hex- of entry, descent and landing, a software feature called
agonally shaped, nearly 1 foot (0.3 meter) in diameter “second chance” has been designed to enable the other
and mounted near the left edge of the rover deck. With side to promptly take control, and in most cases, finish
this antenna, the X-band subsystem is designed to the landing with a bare-bones version of entry, descent
transmit at 160 bits per second or faster to the Deep and landing instructions.
Space Network’s 112-foot-diameter (34-meter-diame-
ter) antennas or at 800 bits per second or faster to the Each rover compute element contains a radiation-hard-
Deep Space Network’s 230-foot-diameter (70-meter- ened central processor with PowerPC 750 architecture:
diameter) antennas. The high-gain antenna, which a BAE RAD 750. This processor operates at up to 200
requires pointing, can be used for either transmitting or megahertz speed, compared with 20 megahertz speed
receiving. The rover low-gain antenna, which does not of the single RAD6000 central processor in each of the
require pointing, is designed primarily for receiving com- Mars rovers Spirit and Opportunity. Each of Curiosity’s
munications from the Deep Space Network. X-band redundant computers has 2 gigabytes of flash memory
reception through the high-gain antenna is anticipated (about eight times as much as Spirit or Opportunity),
as the typical method for daily uplink of commands to 256 megabytes of dynamic random access memory
the rover. and 256 kilobytes of electrically erasable programmable
read-only memory.
The rover UHF antenna, a helix-pattern cylinder mount-
ed high near the right-rear corner of Curiosity is fed by The Mars Science Laboratory flight software monitors
a pair of redundant Electra-Lite radios, which were built the status and health of the spacecraft during all phases
through a partnership between NASA’s Jet Propulsion of the mission, checks for the presence of commands
Laboratory and L-3 Cincinnati Electronics, Mason, to execute, performs communication functions and con-
Ohio. These radios are software-defined, enabling them trols spacecraft activities. The spacecraft was launched
to autonomously adjust their data rate to suit variations with software adequate to serve for the landing and for
in signal strength due to angles and transmission dis- operations on the surface of Mars, as well as during
tance. They use standardized communication protocols the flight from Earth to Mars. The months after launch
for interoperability with all the relay orbiters at Mars, and were used, as planned, to develop and test improved
are especially compatible with the adaptive Electra UHF flight software versions. One upgraded version was
radio on NASA’s Mars Reconnaissance Orbiter. The pri- sent to the spacecraft in May 2012 and installed onto
mary method for the rover’s transmission of data is an- its computers in May and June. This version includes
ticipated to be UHF relay to the Mars Reconnaissance improvements for entry, descent and landing. Another
Orbiter or Mars Odyssey orbiter during two of the op- was sent to the spacecraft in June and will be installed
portunities each Martian day when the orbiters pass in on the rover’s computers a few days after landing, with
the sky above the rover. The European Space Agency’s improvements for driving the rover and using its robotic
Mars Express orbiter also has the capability to serve as arm.
a backup relay.
Rover Navigation
Rover Computing
Two sets of engineering cameras on the rover —
Curiosity has redundant main computers, or rover Navigation cameras (Navcams) up high and Hazard-
compute elements. Of this “A” and “B” pair, it uses one Avoidance cameras (Hazcams) down low — will inform
at a time, with the spare held in cold backup. Thus, at a operational decisions both by Curiosity’s onboard
given time, the rover is operating from either its “A” side autonomy software and by the rover team on Earth.
or its “B” side. Most rover devices can be controlled by Information from these cameras is used for autonomous
either side; a few components, such as the navigation navigation, engineers’ calculations for maneuvering the
camera, have side-specific redundancy themselves. robotic arm and scientists’ decisions about pointing the
The computer inside the rover — whichever side is ac- remote-sensing science instruments.

Mars Science Laboratory Landing 42 Press Kit
Curiosity’s Navcams and Hazcams generate grayscale Each Hazcam has a fisheye lens providing a square field
images that cover red wavelengths centered at about of view 124 degrees wide and tall. The depth of field in
650 nanometers. The cameras themselves are virtu- focus spans from about 4 inches (10 centimeters) to
ally identical to the engineering cameras on Spirit and infinity. Resolution of the Hazcams is 2.1 milliradians per
Opportunity, though Curiosity has redundant cameras pixel on the same type of detector as in the Navcams.
and slightly more powerful heaters for the cameras. At a distance of 33 feet (10 meters), the Hazcam resolu-
Curiosity has a total of 12 engineering cameras, each tion is 0.8 inch (2 centimeters) per pixel. A golf ball at
weighing about 9 ounces (250 grams). that distance would be approximately two Hazcam
pixels across.
Curiosity’s Navcams, paired for stereo imaging, are
installed next to the science payload’s Mast Camera on The redundant pairs of Hazcams are mounted side by
the remote-sensing mast. Curiosity carries two stereo side. On the front, each stereo pair has a baseline of
pairs of Navcams, one pair each connected to the 6.54 inches (16.6 centimeters) between the center of its
rover’s two redundant computers. The Navcams that left eye and center of its right eye. Both the pair linked to
are controlled by and feed imagery to the “A” computer the rover’s “A” computer and the pair linked to the “B”
are mounted directly above the ones linked to the “B” computer are mounted near the bottom center of the
computer. That puts the “A” pair about 6.5 feet (1.99 front face of the chassis, about 27 inches (68 centime-
meters) above the ground when the rover is on hard, ters) above ground level. The rear stereo pairs each have
flat terrain and the cameras are pointed straight out a baseline of 3.9 inches (10 centimeters), the same as
(slightly lower when pointed downward), and the other for both the front and rear hazard-identification cameras
pair 2 inches (5 centimeters) lower. The left and right on Spirit and Opportunity. The rear “A” pair on Curiosity
cameras in each pair are about 16.5 inches (42 centi- is toward the port side of the rear face of the vehicle (on
meters) apart, giving them approximately twice as long the left if a viewer were standing behind the rover and
a stereo baseline as the separation distance of naviga- looking toward it). The rear “B” pair is on the right, or
tion cameras on Spirit and Opportunity. toward starboard. Both pairs are about 31 inches (78
centimeters) above ground level.
Each of the Navcams captures a square field of view
45 degrees wide and tall, comparable to the field of Curiosity’s Hazcams have one-time-removable lens cov-
view of a 37-millimeter-focal-length lens on a 35-mil- ers to shield them from potential dust raised during the
limeter, single-lens reflex camera. The lens focuses rover’s landing. Pyrotechnic devices will remove the lens
the image onto a 1,024-pixel-by-1,024-pixel area of a caps after landing. The Navcams gain protection from
charge-coupled device (CCD) detector. This yields a the stowed position of the remote-sensing mast during
resolution of 0.82 milliradians per pixel — for example, the landing; they do not have lens covers.
0.8 inch (2 centimeters) per pixel at a distance of
82 feet (25 meters), enough to resolve a golf ball at that Different navigation modes for rover drives use im-
distance as a circle about two Navcam pixels wide. ages from the engineering cameras in different ways.
The depth of field achieved by the fixed-aperture f/12 Techniques include “blind” driving, hazard avoidance
Navcams keeps anything in focus from a distance of and visual odometry. The set of commands developed
about 20 inches (0.5 meter) to infinity. by rover planners for a single day’s drive may include a
combination of these modes.
Curiosity has four pairs of Hazcams: two redundant
pairs on the front of the chassis and two redundant When using the blind-drive mode, rover planners have
pairs on the rear. The rover can drive backwards as sufficient local imaging from the engineering cameras or
well as forward, so both the front and rear Hazcams Mast Camera to determine that a safe path exists, free
can be used for detecting potential obstacles in the of obstacles or hazards. They command the rover to
rover’s driving direction. The front Hazcams also provide drive a certain distance in a certain direction. In a blind
three-dimensional information for planning motions of drive, the rover’s computer calculates distance solely
the rover’s robotic arm, such as positioning of the drill or from wheel rotation; one full turn of a wheel with no slip-
scoop for collecting samples. page is about 62 inches (157 centimeters) of driving. It
does not check imagery from the engineering cameras
to assess the slippage.

Mars Science Laboratory Landing 43 Press Kit
When the rover planners cannot determine that a path set of driving commands, rover planners can set the
is free of obstacles, they can command driving that intervals at which the rover pauses for visual-odometry
uses hazard avoidance. Besides using this hazard checks, as suited to the type of terrain being traversed.
avoidance in rougher terrain, they might use it for an ad- A slip limit can be set so that if the rover calculates that
ditional segment of driving beyond a blind drive on the it is slipping in excess of that amount, it will stop driving
same day. Hazard avoidance requires the rover to stop for the day. The mode of using visual odometry checks
frequently to acquire new stereo imaging in the drive at intervals several times the rover’s own length is called
direction with the engineering cameras and analyze the slip-check, to differentiate it from full-time visual odom-
images for potential hazards. The rover makes decisions etry with sideways-looking stops as frequently as a frac-
based on its analysis of the three-dimensional informa- tion of the rover’s length.
tion provided by the stereo imaging. Rover planners set
variables such as how frequently to stop and check, Navigation modes differ significantly in the fraction of
which cameras to use, and what type of decision the time spent with wheels in motion versus stopped for
rover makes in response to a hazard detection (whether imaging and analysis of the images.
to choose a path around it or stop driving for the day).
Curiosity can incorporate other safety features in each
Hazard avoidance can be supplemented with visual drive, such as tilt limits. The rover’s inertial measure-
odometry. Visual odometry uses Navcam images made ment unit, which incorporates gyroscopes, provides
with the cameras pointed to the side of the route being information about changes in tilt. This and other infor-
driven. By pausing at intervals during the drive to take mation about the rover’s attitude, or orientation, serve
these images, the rover can compare the before-and- in use of the arm and the science instruments, and in
after situation for each segment of the drive. It can pointing the high-gain antenna, as well as in navigation.
recognize features in the images and calculate how far it
has actually traveled during the intervening drive seg- Rover Thermal
ment. Any difference between that distance and the dis-
tance indicated from wheel rotation is an indication that Curiosity’s thermal control system was designed to
the wheels are slipping against the ground. In the day’s enable the rover to operate far from the equator so that

The rover’s heat rejection system has a pumped- Silicon chips mounted onto Curiosity’s deck bear the
fluid loop that can deliver heat from the multi-mission names of people who participated in the “Send Your
radioisotope thermoelectric generator when the core Name to Mars” program online. Each chip is about the
electronics need heating and take heat away from the size of a dime. More than 1.24 million names were sub-
core if the rover is becoming too warm. Pacific Design mitted online. These names have been etched into sili-
Technologies Inc., Goleta, Calif., built the pump. con using an electron-beam machine used for fabricat-
The fluid loop runs through an avionics mounting plate ing microdevices at NASA’s Jet Propulsion Laboratory. In
inside the insulated warm electronics box of the rover addition, more than 20,000 visitors to JPL and NASA’s
chassis. The multi-mission radioisotope thermoelectric Kennedy Space Center wrote their names on pages
generator cools passively with its radiator fins when its that have been scanned and reproduced at microscopic
heat is not needed for warming the rover. For heat- scale on another chip.

Mars Science Laboratory Landing 45 Press Kit
Curiosity’s Landing Site
The Mars Science Laboratory mission will place the ing water, some of it would have pooled inside Gale.
rover Curiosity at the foot of a mountain of sedimentary Observations from orbit that add evidence of a wet
strata, or layers, inside Gale Crater. The landing site at history include water-related clay and sulfate minerals
4.6 degrees south latitude, 137.4 degrees east longi- in the lower layers of the mound, and textures higher
tude will give the rover access to a field site with science on the mound where it appears that mineral-saturated
targets both on the crater floor beside the mountain and groundwater filled fractures and deposited minerals.
in the lower layers of the mountain.
Stratification in the mound suggests it is the surviving
Gale Crater spans 96 miles (154 kilometers) in diameter, remnant of an extensive sequence of deposits that
giving it an area about the equivalent of Connecticut and were laid down after the impact that excavated the
Rhode Island combined. It holds a mound, informally crater more than 3 billion years ago. Each geological
named Mount Sharp, rising about 3 miles (5 kilometers) layer, called a stratum, is formed after the layer beneath
above the crater floor, which is higher than Mt. Rainier it and before the one above it. The stack of layers that
rises above Seattle. The slopes of Mount Sharp are forms Mount Sharp offers a history book of sequential
gentle enough for Curiosity to climb, though during the chapters recording environmental conditions when
prime mission of one Martian year (98 weeks), the rover each stratum was deposited. This is the same principle
will probably not go beyond some particularly intriguing of geology that makes the strata exposed in Arizona’s
layers near the base. Grand Canyon a record of environmental history on
Earth. For more than 150 years, geologists on Earth
Gale sits at a low elevation relative to most of the surface have used stacks of strata from globally dispersed loca-
of Mars, suggesting that if Mars ever had much flow- tions to piece together a record of Earth history.

Locations of landing sites for Curiosity and previous Mars rovers and landers

Mars Science Laboratory Landing 46 Press Kit
Mount Sharp’s stack of layers is much taller than the needed to qualify as safe for landing. The mission’s tech-
stack admired in the Grand Canyon. It is a closer nologies for atmospheric entry, descent and landing give
match to the amount of layering exposed in Mars’ the spacecraft about a 99-percent probability of landing
Valles Marineris, the largest canyon in our solar system. within an ellipse 12.4 miles (20 kilometers) by 15.5 miles
Therefore, Mount Sharp may offer one of the thickest (25 kilometers), as calculated during the site-selection
continuous sequences of strata in the solar system. On process. That is about one-third the size of the landing
Earth, the thickest sequences of strata that also contain ellipses for Mars rovers that landed in 2004. Curiosity
a diversity of materials are the best records of Earth’s his- was designed and built to be able to drive far enough to
tory. Like the most complete copy of an ancient manu- get outside of its landing ellipse during its prime mis-
script, they can be used to decode and tie together less sion. While Curiosity was on its way from Earth to Mars,
complete records from around the globe. It is hoped that continuing analysis of the entry, descent and landing
the record at Gale Crater will be just such a key reference variables led to confidence in even higher precision.
for deciphering Mars’ global history. This enabled shrinking the landing ellipse to about 4 by
12 miles (7 by 20 kilometers) and moving the center
Gale Crater was named in 1991 for Australian as- target closer to Mount Sharp.
tronomer and banker Walter F. Gale (1865–1945), who
discovered several comets and drew maps of Mars and The slopes of Mount Sharp are too steep for the rover
Jupiter. Coincidentally, the mound inside Gale, when to land safely on the mountain. The science targets
viewed from orbit, resembles the shape of Australia. initially identified for the rover to investigate are in the
lower layers of the mountain, requiring the rover to drive
Curiosity’s Project Science Group chose the informal outside the landing ellipse to get to the science targets.
name Mount Sharp in early 2012 as a tribute to geolo- Subsequent observations and analysis have identified
gist Robert P. Sharp (1911–2004). Sharp was a founder additional science targets within the landing ellipse.
of the field of planetary science, an influential teacher of The pace at which Curiosity gets to the features of high
many current leaders in the field, and team member for science interest inside and outside of the ellipse will
NASA’s first few Mars missions. He taught geology at the depend on findings and decisions made after landing,
California Institute of Technology (Caltech), in Pasadena, including the possibility of identifying targets not yet
from 1948 until past his retirement. known. Getting to key destinations at lower layers of
Mount Sharp may take a large fraction of the 98-week
NASA’s choice of the landing site in Gale Crater in July prime mission. The route may involve navigation through
2011 followed a five-year process that considered about some challenging terrains such as sand dunes, hills and
60 sites and involved about 150 Mars scientists in a canyons.
series of public workshops. Four finalist sites identified in
2008 were mapped and examined so extensively from In Curiosity’s field site — encompassing accessible ar-
orbit that they have become four of the best-studied eas inside and outside of the landing ellipse — features
places on Mars. The detail in images taken by the High that make Gale appealing to the science team include:
Resolution Imaging Science Experiment camera on
NASA’s Mars Reconnaissance Orbiter, for example, • An alluvial fan extending into the landing ellipse from
reveals virtually every individual boulder big enough the crater wall to the north holds material shed from
to spoil a landing. Mineral mapping by the Compact the crater wall and likely carried by water.
Reconnaissance Imaging Spectrometer on the same
orbiter and the OMEGA spectrometer on the European • Down slope, or southward, from the alluvial fan lies
Space Agency’s Mars Express identified mineral evi- an exposure of hard, light-toned rock. The min-
dence of wet histories at all four sites. All four finalist sites eral composition of this area is unidentified so far.
qualified as safe for landing, so the selection could be Curiosity could investigate a hypothesis that this
made based on the sites’ scientific appeal. exposure is sedimentary rock formed in interaction
with water, such as salts left by the drying of a lake.
The guided entry technology enabling the Mars Science Some relatively fresh, small craters in this part of the
Laboratory to land more precisely than previous Mars crater floor may provide access to material that has
missions, coupled with Curiosity’s driving capability, not experienced long exposure to the radiation envi-
meant that, for the first time, the main science destina- ronment affecting chemistry at the Martian surface.
tion for a Mars mission could be outside of the area that

Mars Science Laboratory Landing 47 Press Kit
Landing ellipse in Gale Crater, in overhead view with north at the top

Curiosity’s landing area and surrounding terrain at Gale Crater, looking toward the southeast

Mars Science Laboratory Landing 48 Press Kit
• Among the exposures in the lower portion of Mount One important capability of Curiosity’s science payload
Sharp are packages of strata that contain clay min- is to check for the presence of ingredients for life, includ-
erals, strata that contain sulfate salts and strata that ing the carbon-based building blocks of biology called
contain both. Clays and sulfates both result from organic compounds. Long-term preservation of organic
wet environments. The differences in mineral com- compounds requires special conditions.
position from one package of strata to the next can
provide information about changes in environments Clays and sulfate-rich deposits such as the ones
that may have been favorable for microbial life. Curiosity will investigate in Gale Crater can be good at
latching onto organic chemicals and protecting them
• Curiosity’s analysis of the exposed minerals will from oxidation. Another factor in long-term preservation
provide confirmation of orbiter-based predictions for of organics on Mars is protection from natural radiation
the distribution and abundance of similar minerals that is more intense than what reaches Earth’s surface.
to be present over vast parts of Mars. In this regard, Radiation may gradually destroy organics inside rocks
Curiosity will provide important ground truth of hy- at the surface, but Gale also offers rocks exposed by
potheses generated by previous missions. relatively recent small-crater impacts.

• The sulfate salts retain trace amounts of water in Gale offers these attractive targets at which to check for
their mineral structure. Curiosity can monitor how organic compounds. Finding organics is still a long shot,
some of that water is released into the atmosphere but this chosen field site also offers records of multiple
during warmer hours of the day and reabsorbed by periods in Mars history, grist for the mission’s investiga-
the salts during colder hours. These measurements tion of environmental changes on Mars, with strong
would provide information about the modern water prospects for identifying habitable environments.
cycle on Mars.
Should Curiosity continue to be in working condition
• Canyons cut into the northern flank of Mount Sharp following the prime mission, an extended mission could
resulted from flow of water long after the lower lay- continue the investigation by exploring higher, younger
ers of the mountain had accumulated. The canyon- layers of Mount Sharp.
cutting environment could have been a separate
habitable environment from the environment at
the time the clay-containing and sulfate-containing
layers formed. Analysis of material deposited at the
mouths of the canyons could provide information
about that later environment.

• Extensive networks of fractures in the upper parts of
the sulfate-bearing strata are filled with minerals that
betray circulation of groundwater. These fracture
networks would represent yet a different, subsurface
habitable environment. The presence of minerals
lining these fractures indicates where Curiosity might
conduct analyses to look for organic compounds.

Mars Science Laboratory Landing 49 Press Kit
Recent, Current and Upcoming Missions
Building on scientific discoveries and lessons from had begun a fourth extension and was five days shy of
past and ongoing missions, NASA’s Mars Exploration the 10th anniversary of its launch when it last communi-
Program is working to establish a sustained observa- cated with Earth. Mars Global Surveyor returned more
tional presence at Mars. This includes orbiters that view than 240,000 camera images, 206 million spectrometer
the planet from above and act as telecommunications measurements and 671 million laser-altimeter shots.
relays, surface-based mobile laboratories, robots that Some of the mission’s most significant findings include:
probe below the planet’s surface, and, ultimately, mis- discovering extensive layering of the planet’s crust;
sions that return soil and rock samples to Earth and discovering ancient deltas; discovering channels, a few
prepare for human landing. of which exhibit modern activity suggesting modern
liquid water; identifying concentrations of a mineral that
With international cooperation, the long-term program is often forms under wet conditions, leading to selection of
guided by compelling questions about Mars and de- one large deposit as the landing area for NASA’s Mars
veloping technologies to make missions possible with Exploration Rover Opportunity; laser-altimeter obser-
available resources. The program’s strategy is to seek to vations producing a nearly global map of the planet’s
uncover profound insights into Mars’ past and present topography, quantifying altitudes and slopes, and
environments, the roles and abundance of water, and characterizing myriad craters, including many eroded or
the potential for past or present habitats suitable for the buried craters too subtle for previous observation; com-
existence of life. piling extensive evidence for the role of dust in reshaping
the recent Martian environment; and detecting localized
The following are the most recently completed, ongoing remnant magnetic fields, proof that Mars once had a
and near-term future Mars missions of exploration by global magnetic field like Earth’s, shielding the surface
NASA and its international partners: from deadly cosmic rays and slowing loss of volatiles
to space. This orbiter provided details used to evaluate
Mars Pathfinder (December 1996 – March 1998): the risks and attractions of potential landing sites for
The first completed mission in NASA’s Discovery the Phoenix Mars Lander and the two Mars Exploration
Program of low-cost planetary missions with highly Rovers. It also served as a communications relay for the
focused scientific goals, Mars Pathfinder set ambitious Mars Exploration Rovers during and after their landings.
objectives and surpassed them. This lander released
its Sojourner rover on the Martian surface and returned Mars Odyssey (April 2001 – present): This NASA
2.3 billion bits of information from instruments on the orbiter’s prime mapping mission began in March 2002.
lander and the rover. The information included more Its suite of gamma-ray spectrometer instruments soon
than 17,000 images, more than 15 chemical analyses of provided strong evidence for large quantities of frozen
rocks and soil, and extensive data on winds and other water mixed into the top layer of soil in the 20 percent of
aspects of weather. The observations suggest that early the planet near its north and south poles. Subsequently,
Mars may have been more Earth-like with liquid water on a site in this permafrost terrain became the destina-
its surface and a thicker atmosphere than it has today. tion for the Phoenix Mars Lander. Odyssey’s camera
The mission functioned on the Martian surface for about system, which examines the planet in both visible-light
three months, well beyond the planned lifetimes of and infrared wavelengths, has identified minerals in
30 days for the lander and seven days for the rover. rocks and soils and has compiled the highest-resolution
global map of Mars. Nighttime infrared imaging provides
Mars Global Surveyor (November 1996 – information about how quickly or slowly surface features
November 2006): During its primary mapping mission cool off after sunset, which gives an indication of where
from March 1999 through January 2001, NASA’s Mars the surface is rocky and where it is dusty. Odyssey’s
Global Surveyor collected more information than any instruments have monitored the Mars atmosphere for
previous Mars project. The orbiter continued to examine more than a decade, including the tracking of non-con-
Mars’ surface and monitor its global weather patterns densable gases such as argon as tracers of atmospher-
through three mission extensions, successfully operat- ic transport. Odyssey has also monitored high-energy
ing longer than any previous spacecraft sent to Mars. It radiation at orbital altitudes to help characterize the en-

Mars Science Laboratory Landing 50 Press Kit
vironment that future missions, including possible human Mars Exploration Rover Opportunity (July 2003
ones, will experience. Odyssey’s observations helped - present): This rover was sent to a flat region named
evaluate potential landing sites for the Mars Exploration Meridiani Planum, where the spectrometer on Mars
Rovers, Phoenix and Curiosity. Relays via this orbiter Global Surveyor had discovered a large exposure of the
have been the main way for the rovers and Phoenix to mineral hematite — which often forms in the presence
send information to Earth; more than 95 percent of rover of water. On Jan. 25, 2004, Opportunity landed inside a
data has been returned via this communications work- crater only 72 feet (22 meters) in diameter and immedi-
horse. Odyssey is now the longest-working spacecraft ately saw exposed bedrock in the crater’s inner slope.
ever sent to Mars. It will continue to map the planet while During the next few weeks, the rover’s examination
providing relay support for Curiosity. of that outcrop settled the long-running debate about
whether Mars ever had sustained liquid water on its sur-
Mars Exploration Rover Spirit (June 2003 – March face. Composition and textures showed that the rocks
2010): The first of NASA’s twin Mars Exploration Rovers not only had been saturated with water, but had actually
to land on Mars, Spirit was a mobile robotic field geolo- been laid down under gently flowing surface water.
gist sent to examine clues about the planet’s environ- For six months beginning in June 2004, Opportunity
mental history — particularly the history of water — at a examined deeper layers of rock inside a stadium-size
carefully selected site. Each rover’s mission was planned crater, Endurance, about half a mile (700 meters) from
to run for three months on Mars, but each rover worked the landing site. The wall-rock layers had all soaked in
for years. Spirit explored inside Gusev Crater, a highly water, but textures in some showed that periods of dry,
eroded crater 95 miles (150 kilometers) in diameter. wind-blown deposition alternated with periods when
Orbital images suggested Gusev may have once held a water covered the surface. After examining its own jet-
lake fed by inflow from a large valley network funneling tisoned heat shield and a nickel-iron meteorite near this
into the crater from highlands to the south. Spirit landed crater, Opportunity drove more than 4 miles (6 kilome-
Jan. 4, 2004, on a flat volcanic flood-plain pocked ters) southward to reach an even larger and deeper
with small craters and strewn with loose rocks. There, crater, Victoria. Here, it examined geological evidence
the rover found basaltic rocks only slightly altered by of similar environmental conditions from a greater span
exposure to moisture. By June 2004, well into its first of time. The presence of sulfur-rich material throughout
extended mission, Spirit had driven to a range named Opportunity’s study area indicates acidic watery envi-
the Columbia Hills, about 1.6 miles (2.6 kilometers) from ronments. In mid-2008, Opportunity set off toward a
the landing site, in a quest to find exposed bedrock. crater 14 miles (22 kilometers) in diameter, Endeavour,
Exploring in the hills, Spirit discovered a profusion of where orbital observations have detected water-related
rocks and soils bearing evidence of extensive exposure clay minerals, different from any Opportunity has seen
to water, including the iron-oxide-hydroxide mineral so far and indicative of less-acidic watery environments.
goethite and hydrated sulfate salts. It found an outcrop In August 2011, with a total driving odometry of more
rich in carbonate, evidence for wet conditions that were than 21 miles (34 kilometers), the rover reached the rim
not acidic. Textures and compositions of materials at of Endeavour Crater to start a new phase of its explora-
a low plateau between hills indicated an early era on tion of Mars. There it found water-deposited veins of
Mars when water and hot rocks interacted in explosive gypsum, demonstrating once more the value of mobility
volcanism. By driving with one immobile wheel whose and longevity.
motor had worn out after three years on Mars, Spirit
serendipitously plowed up a hidden deposit of nearly Mars Express (June 2003 – present): This is a
pure silica. This discovery indicates that the site once European Space Agency orbiter with NASA participa-
had hot springs or steam vents, which are environments tion in two of its seven investigations: a ground-pene-
that, on Earth, teem with microbial life. In June 2009, trating radar, and a tool for studying how the solar wind
Spirit became embedded in a patch of fine-grained removes water vapor from Mars’ outer atmosphere.
material and was unable to extract itself after a second The spacecraft has been returning color stereo images
wheel stopped working. Prevented from parking itself in and other data since January 2004 after entering orbit
a position favorable for its solar array to generate energy, in late December 2003. Its spectrometer for visible
Spirit was apparently unable to survive the long southern and near-infrared wavelengths found deposits of clay
winter, as no further communications were received. minerals indicating a long-ago wet environment that
was less acidic than the one that produced the miner-
als studied by Opportunity. Scientists working with this

Mars Science Laboratory Landing 51 Press Kit
and similar data from the Mars Reconnaissance Orbiter Mars is still a dynamic world. The orbiter’s observations
have proposed a sequence of globally distributed water have identified sites with high potential for future scien-
environments very early in Mars’ history, moving from tific discovery. In addition, the orbiter’s high-resolution
less to more acidic environments. Meanwhile, scientists cameras can reveal hazards to landing and roving
working with data from a thermal infrared spectrometer spacecraft, such as rocks and steep slopes, while its
found indications of methane in Mars’ atmosphere by atmospheric monitors characterize the environment that
averaging millions of spectra to improve signal-to-noise can be encountered during landing and operations on
ratio. Scientists presently believe that this gas would the surface. Observations by the Mars Reconnaissance
break down too rapidly to be detectable unless there Orbiter enabled the Phoenix mission to choose a land-
is an active source, either biological or non-biological, ing site less rocky than one previously considered. The
maintaining its concentration in the atmosphere. These orbiter has examined potential landing sites for Mars
discoveries have important implications for the habitabil- Science Laboratory and will serve as a relay asset during
ity of Mars, past and present. Since deployment of the the landing and surface operations of Curiosity.
radar antenna in June 2005, the spacecraft has exam-
ined ice-rich layered deposits covering the polar regions. Phoenix Mars Lander (August 2007 – November
2008): In 2001, NASA announced a new program of
Mars Reconnaissance Orbiter (August 2005 – competitively proposed and selected missions to Mars:
present): This multipurpose spacecraft is examining the Mars Scout missions. The Phoenix Mars Lander pro-
surface, subsurface and atmosphere of Mars in unprec- posal, submitted by a team led by Peter Smith of the
edented detail. It began its primary science investigations University of Arizona, Tucson, was selected out of 25
in November 2006, following 426 carefully planned dips proposals in 2003 to be the one developed for launch in
into the top of Mars’ atmosphere to adjust the size and 2007. The mission sent a stationary lander with a robotic
shape of its orbit after arriving at Mars in March 2006. digging arm and suite of science instruments to study
Specifically engineered to return the vast volumes of data the summer environment in a far-northern zone. Phoenix
generated by the high spatial resolution of its imaging confirmed and examined deposits of underground water
cameras and spectrometer, the orbiter has returned ice detected from orbit by Mars Odyssey. It identified a
more than three times as much data as the combined mineral called calcium carbonate that suggested occa-
total from all other space missions that have traveled sional presence of thawed water. The lander also found
farther than the moon. NASA’s Deep Space Network soil chemistry with significant implications for life and ob-
antennas received more than 130 terabytes of data — served falling snow. The mission’s biggest surprise was
including more than 70,000 images — from the six sci- the discovery of perchlorate, an oxidizing chemical on
ence instruments on Mars Reconnaissance Orbiter dur- Earth that is food for some microbes and potentially toxic
ing the mission’s first five years at Mars. The mission has for others, and which can lower the freezing point of
illuminated three very different periods of Mars’ history. Its liquid water by tens of degrees. It completed its planned
observations show that different types of watery environ- three months of operation on Mars and worked two
ments formed extensive deposits of water-related miner- extra months before the anticipated seasonal decline in
als — including clays, sulfates and carbonates — across solar energy at its high latitude ended the mission.
the planet early in Mars’ history. In more recent times,
water appears to have cycled as a gas between polar Mars Atmosphere and Volatile Evolution
ice deposits and lower-latitude deposits of ice and snow. Mission, or MAVEN (for launch in 2013): The sec-
Radar observations reveal internal, episodic patterns of ond Mars Scout mission, selected from 26 competitive
layering probably connected to cyclical variations in the proposals in 2007, will explore the planet’s upper atmo-
tilt of the planet’s rotation axis and the elliptical nature of sphere, ionosphere and interactions with the sun and
its orbit. These cycles modulate the solar heating of the solar wind. Various evidence suggests that Mars was a
poles to a much larger degree than occurs for Earth, wetter planet early in its history. Where has that water
with its ice ages, over periods of thousands to a few gone? Scientists will use MAVEN data to determine the
million years. Radar has also revealed a thick deposit of role that loss of volatile compounds, such as carbon
carbon-dioxide ice buried in the south polar cap, which, dioxide and water, from the Mars atmosphere to space
if released into the atmosphere, would nearly double has played through time, giving insight into the history
the amount of gas in the atmosphere today. With ob- of Mars’ atmosphere and climate, liquid water, and
servations of new craters, avalanches and dust storms planetary habitability. The principal investigator is Bruce
occurring even now, the orbiter has shown that modern Jakosky, University of Colorado, Boulder.

Mars Science Laboratory Landing 52 Press Kit
Beyond 2016: In early 2012, NASA announced an ini- straints. This group will submit a report to NASA in late
tiative to develop a strategy for NASA’s Mars Exploration summer. NASA will use it to create a reformulated Mars
Program in light of new funding constraints. The initial Exploration Program, which will be reflected in the presi-
focus is on a possible 2018–2020 robotic mission that dent’s Fiscal Year 2014 budget request to be released
will not only conduct important science, but will incorpo- in February 2013. The reformulated Mars program
rate objectives and goals of NASA’s human exploration is expected to advance the intentions in the National
and technology programs. NASA solicited ideas to be Research Council’s decadal survey for planetary sci-
incorporated into the planning process for Mars explora- ence, which puts Mars sample return as a top scientific
tion, and more than 400 concepts and abstracts were priority. The planning initiative also considers related
submitted for presentation at a June 2012 public con- objectives of NASA’s Office of the Chief Technologist
ference at the Lunar and Planetary Institute in Houston. and NASA’s Human Exploration and Operations Mission
The Mars Program Planning Group, an independent Directorate. The Mars program will incorporate elements
group formed to develop concepts and approaches of advanced research and technologies in support of
for future exploration of Mars for NASA, is considering a logical sequence of missions to answer fundamental
inputs from the conference and taking into consideration scientific questions and ultimately support future human
budgetary, programmatic, scientific and technical con- exploration of Mars.

Mars Science Laboratory Landing 53 Press Kit
Mars Science: A Story of Changes
As the world in 1965 eagerly awaited results of the first intrigued by the possibility that life in some form —
spacecraft flyby of Mars, everything we knew about the perhaps very simple microbes — may have gained a
Red Planet was based on what sparse details could be foothold in ancient times when Mars was wetter, if not
gleaned by peering at it from telescopes on Earth. Since warmer. It is not unthinkable that life in some form could
the early 1900s, popular culture had been enlivened by persist today in underground springs warmed by heat
the notion of a habitable neighboring world crisscrossed vents around smoldering volcanoes, or even beneath
by canals and, possibly, inhabited by advanced life the thick ice caps. To investigate those possibilities,
forms that might have built them — whether friendly or NASA’s productive strategy has been to learn more
not. Astronomers were highly skeptical about the ca- about the history of water on Mars: How much was
nals, which looked more dubious the closer they looked. there? How long did it last? Where are formerly wet en-
About the only hard information they had on Mars was vironments that make the best destinations for seeking
that they could see it had seasons with ice caps that evidence of past life? Where might there be wet environ-
waxed and waned, along with seasonally changing ments capable of sustaining life today?
surface markings. By breaking down the light from Mars
into colors, they learned that its atmosphere was thin The consensus strategy for answering those questions
and dominated by an unbreathable gas, carbon dioxide. uses a balance of examining selected sites in great
detail while also conducting planet-wide surveys to
The past four decades have revolutionized that view. provide context for interpreting the selected sites. This
First, hopes of a lush, Earth-like world were deflated enables researchers to extrapolate from the intensively
when Mariner 4’s flyby on July 15, 1965, revealed large investigated sites to regional and global patterns, and to
impact craters, like craters that cover Earth’s barren, life- identify which specific sites make the best candidates
less moon. Those holding out for Martians were further for targeted examination.
discouraged when NASA’s two Viking landers were sent
to the surface in 1976 equipped with a suite of chem- One way this balance works is in the combination
istry experiments that turned up no conclusive sign of punch of orbital and surface missions. Mineral map-
biological activity. Mars as we came to know it was cold, ping by NASA’s orbiting Mars Global Surveyor identified
nearly airless and bombarded by hostile radiation from a hematite deposit that made Meridiani Planum the
both the sun and from deep space. selected landing site for NASA’s Mars Exploration Rover
Opportunity. The hematite suggested a possible water
Since then, however, new possibilities of a more hospi- history. Opportunity’s examination of the composition
table Martian past have emerged. Mars is a much more and fine structure of rocks where it landed confirmed
complex body than Earth’s moon. Scientists scrutinizing that the site had had surface and underground water,
pictures from the orbiters of the 1970s detected surface and added details about the acidity of the water and the
features potentially shaped by liquid water, perhaps alternation of wet and dry periods at the site. Meanwhile,
even the shoreline of an ancient ocean. Eight successful halfway around the planet at Gusev Crater, the Spirit
Mars missions since the mid-1990s have advanced the rover found evidence of materials altered in an ancient
story. Accumulated evidence shows that the surface of hydrothermal system. This “ground truthing” by the rover
Mars appears to be shaped by flowing water in hun- improves interpretation of current orbiters’ observations
dreds of places; that some Mars rocks formed in water; of the surrounding region. Conversely, orbiters’ observa-
that significant amounts of water as ice and in hydrated tions add context for understanding how the environ-
minerals still make up a fraction of the top surface layer ment that landing-site rocks reveal about a particular
of Mars in many areas; and that water may, even today, place and time fits into a broader history.
occasionally emerge from the ground to flow briefly
before freezing or evaporating. Similarly, the Phoenix Mars Lander investigated a site
with intriguing characteristics discovered from orbit.
Although it appears unlikely that complex organisms Spectrometers on NASA’s Mars Odyssey orbiter found
similar to advanced life on Earth could have existed evidence of copious water ice within the top 3 feet
on Mars’ comparatively hostile surface, scientists are (1 meter) of the surface in high-latitude and some mid-

Mars Science Laboratory Landing 54 Press Kit
latitude regions. Phoenix landed at a far-northern site known for the “Tarzan” series, also entertained young
and confirmed the presence of plentiful water ice just readers with tales of adventures among the exotic
beneath the surface. In the soil above the ice, Phoenix inhabitants of Mars, which he called Barsoom.
found a chemical called perchlorate, which could serve
as an energy source for microbes and as a potent anti- Fact began to turn against such imaginings when the
freeze enabling water to be liquid at low temperature. first robotic spacecraft were sent to Mars in the 1960s.
Pictures from the 1965 flyby of Mariner 4 and the 1969
As another example of the synergy among Mars space- flybys of Mariner 6 and 7 showed a desolate world,
craft, NASA’s Mars Reconnaissance Orbiter, which pocked with impact craters similar to those seen on
reached Mars in 2006, found a less rocky, safer land- Earth’s moon. Mariner 9 arrived in 1971 to orbit Mars
ing site for Phoenix. The orbiter also examined more for the first time, but showed up just after an enormous
than 30 potential landing sites for the Mars Science dust storm had engulfed the entire planet. When the
Laboratory. Four finalist sites were examined in thor- storm died down, Mariner 9 revealed a world that,
ough detail to identify specific mineral deposits of inter- while partly crater-pocked like Earth’s moon, was much
est and potential landing hazards down to the scale of more geologically complex, complete with gigantic
individual rocks before Gale Crater was chosen as the canyons, volcanoes, dune fields and polar ice caps.
landing site. This first wave of Mars exploration culminated in the
Viking mission, which sent two orbiters and two land-
The Mars Science Laboratory is NASA’s first astrobiol- ers to the planet in 1975. The landers carried a suite of
ogy mission to Mars since the Viking landers. One goal experiments that conducted chemical tests to detect
of NASA’s Astrobiology Program is to determine the life. Most scientists interpreted the results of these tests
history of any environment having liquid water, other as negative, deflating hopes of identifying another world
chemical ingredients of life, and energy sources that where life might be or have been widespread. However,
might have sustained living systems. Astrobiology’s Viking left a huge legacy of information about Mars that
investment in Mars exploration is geared toward iden- fed a hungry science community for two decades.
tifying, categorizing and understanding locations on
Mars that may have once supported habitable environ- The science community had many other reasons for
ments. This includes developing tools and techniques being interested in Mars, apart from the direct search
for identifying mineralogical and physical signs of liquid for life. The next mission on the drawing boards con-
water, biosignatures and chemical evidence of ancient centrated on a study of the planet’s geology and climate
habitats. using advanced orbital reconnaissance. Over the next
20 years, however, new findings in laboratories and in
Myths and Reality extreme environments on Earth came to change the
way that scientists thought about life and Mars.
Mars caught public fancy in the late 1870s, when Italian
astronomer Giovanni Schiaparelli reported using a tele- One was the 1996 announcement by a team from
scope to observe “canali,” or channels, on Mars. A pos- Stanford University and NASA’s Johnson Space Center
sible mistranslation of this word as “canals” may have that a meteorite believed to have originated on Mars
fired the imagination of Percival Lowell, an American contained what might be the fossils of ancient bacteria.
businessman with an interest in astronomy. Lowell This rock and other Mars meteorites discovered on sev-
founded an observatory in Arizona, where his observa- eral continents on Earth appear to have been blasted
tions of Mars convinced him that the canals were dug off Mars by asteroid or comet impacts. The evidence
by intelligent beings — a view that he energetically that they are from Mars comes from gases trapped
promoted for many years. in them that unmistakably match the composition of
Mars’ atmosphere as measured by the Viking landers.
By the turn of the last century, popular songs envi- Many scientists have questioned the conclusions of the
sioned sending messages between worlds by way of team announcing the discovery of possible life in one
huge signal mirrors. On the dark side, H.G. Wells’ 1898 Martian meteorite, but if nothing else, the mere pres-
novel “The War of the Worlds” portrayed an invasion of ence of organic compounds in the meteorites increases
Earth by technologically superior Martians desperate for the odds of life forming at an earlier time on a wetter
water. In the early 1900s novelist Edgar Rice Burroughs, Mars. The debate has also focused attention on what

Mars Science Laboratory Landing 55 Press Kit
types of experiments would be most useful for assessing on time scales of hundreds of thousands to a few million
whether an extraterrestrial site or sample has ever held years. Mars’ tilt varies much more than Earth’s.
anything alive.
NASA’s Mars Exploration Rover Opportunity established
Another development shaping ideas about extrater- that rocks in at least one part of Mars were formed un-
restrial life was a string of spectacular findings on how der flowing surface water billions of years ago. Minerals
and where life thrives on Earth. The fundamental re- present indicate the ancient water was very acidic.
quirements for life as we know it today are liquid water, Halfway around the planet, Opportunity’s twin, Spirit,
organic compounds and an energy source for synthesiz- found a carbonate deposit offering evidence for a wet
ing complex organic molecules. In recent years, it has environment that was less acidic and found a nearly
become increasingly clear that life can thrive in settings pure silica deposit formed by a hot spring or steam vent.
much harsher than what we as humans can experience. Either of those long-ago environments deduced from
Spirit’s observations could have been even more favor-
In the 1980s and 1990s, biologists found that microbial able for microbial life than the conditions that left the
life has an amazing flexibility for surviving in extreme clues found by Opportunity during Opportunity’s first
environments — niches that by turn are extraordinarily seven years on Mars. In 2011, the long-lived Opportunity
hot, or cold, or dry, or under immense pressures — that also found veins of gypsum deposited by water that
would be completely inhospitable to humans or com- might not have been acidic.
plex animals. Some scientists even deduce that life on
Earth may have begun at hot vents far under the ocean’s The European Space Agency’s Mars Express has identi-
surface. fied exposures of clay minerals that probably formed
in long-lasting, less-acidic wet conditions even earlier
This, in turn, had its effect on how scientists thought in Mars history than the conditions that produced the
about Mars. Martian life might not be so widespread that minerals examined by Opportunity through 2010. Mars
it would be readily found at the foot of a lander space- Express and telescopic studies from Earth have found
craft, but it may have thrived billions of years ago in an traces of atmospheric methane at Mars that might come
underground thermal spring or other hospitable environ- from volcanic or biological sources. A radar instrument
ment. Or it might still exist in some form in niches below co-sponsored by NASA and the Italian Space Agency
the currently frigid, dry, windswept surface, perhaps on the European orbiter has assessed the thickness and
shielded in ice or in liquid water aquifers. water content of icy layers covering Mars’ south polar
region, yielding an estimate that the quantity of water fro-
Each successful Mars mission uncovers more pages of zen into those icy layers is equivalent to a 36-foot-thick
the planet’s story. After years of studying pictures from (11-meter-thick) coating of the whole planet.
the Mariner 9 and Viking orbiters, scientists gradually
came to conclude that many features they saw sug- Since 2006, NASA’s Mars Reconnaissance Orbiter has
gested that Mars may have been warm and wet in an radically expanded our knowledge of the Red Planet.
earlier era. Observing the planet at the highest spatial resolutions
yet achieved from orbit, this mission has provided copi-
Two decades after Viking, NASA’s Mars Pathfinder ous information about ancient environments, ice-age-
observed rounded pebbles and sockets in larger rocks, scale climate cycles and present-day changes on Mars.
suggesting conglomerates that formed in running water. It has mapped water-related mineral deposits, including
Mars Global Surveyor’s camera detected possible evi- multiple types of clay minerals, in hundreds of locations,
dence for recent liquid water in many settings, including and carbonates in several locales, confirming a story of
hundreds of hillside gullies. That orbiter’s longevity even alteration by water in a diversity of environments early in
allowed before-and-after imaging that showed fresh Martian history and a dramatic change to very acidic wa-
gully-flow deposits in 2005 that had not been present ter in many areas after an era of more neutral conditions.
earlier in the mission. Observations by Global Surveyor
and Odyssey have also been interpreted as evidence With regard to recent Mars history, the Mars Recon-
that Mars is still adjusting from a recent ice age as part of naissance Orbiter has added evidence of ongoing
a repeating cycle of global climate change. The cycle re- climate-change cycles linked to how changes in the tilt
sults from changes in the tilt of the rotational axis of Mars of the planet’s rotation axis alter intensity of sunlight near

Mars Science Laboratory Landing 56 Press Kit
the poles. This evidence includes radar observations of Three Ages of Mars
episodic layering within the polar ice caps and of debris-
covered ice deposits. Other observations have revealed Based on what they have learned from spacecraft mis-
water ice just below the surface in middle latitudes, sions, scientists view Mars as the “in-between” planet
exposed in small craters formed by fresh impacts identi- of the inner solar system. Small rocky planetary bodies
fied in before-and-after observations. These findings and such as Mercury and Earth’s moon apparently did not
their implications for ongoing cycles of climate change have enough internal heat to drive the motion of tectonic
put water ice closer to the equator on modern Mars, in- plates, so their crusts grew cold and static relatively
cluding possibly beneath the Viking 2 Lander, than most soon after they formed when the solar system con-
researchers imagined a few years ago. densed into planets about 4.6 billion years ago. Devoid
of atmospheres, they are riddled with craters that are rel-
Orbital studies in recent years have also revealed some ics of impacts from a period of bombardment when the
processes on Mars very unlike those on Earth related to inner planets were sweeping up remnants of small rocky
temperatures low enough to freeze some of the carbon- bodies that failed to “make it as planets” in the solar
dioxide gas out of the planet’s thin atmosphere, which is system’s early times.
mostly that gas. Carbon-dioxide ice blankets the ground
around whichever pole is in winter. In the spring, sunlight Earth and Venus, by contrast, are larger planets with
penetrates the translucent ice, heating it from below. substantial internal heat sources and significant at-
As the carbon dioxide thaws back into gas, it triggers mospheres. Earth’s surface is continually reshaped by
geyser-like eruptions in some areas and fresh flows of tectonic plates sliding under and against each other and
sand on slopes in other areas. by materials spouting forth from active volcanoes where
plates are ripped apart. Both Earth and Venus have
The surface pressure of the Mars atmosphere varies been paved over so recently that both lack any discern-
over the year as the seasonal carbon-dioxide frost forms ible record of cratering from the era of bombardment in
and then sublimes at each pole in turn. A major finding the early solar system.
by the radar on Mars Reconnaissance Orbiter is a thick,
hidden layer of carbon-dioxide ice deep in the water On the basis of current yet evolving knowledge, Mars
ice that forms the bulk of the south polar ice cap. This appears to stand between those sets of worlds. Like
deposit may contain nearly as much carbon dioxide as Earth and Venus, it possesses many volcanoes, al-
today’s Martian atmosphere. This implies that the total though they probably did not remain active as long as
mass of the atmosphere on Mars can change several counterparts on Earth and Venus. On Earth, a single
fold on time scales of hundreds of thousands of years “hot spot” or plume might form a chain of middling-size
or less. Computer modeling indicates that during larger islands, such as the Hawaiian Islands, as a tectonic
tilt, when summertime solar heating at the poles is more plate slowly slides over it. On Mars, there are appar-
intense, most of the frozen carbon dioxide rejoins the ently no such tectonic plates, at least as far as we know
atmosphere, and that during smaller tilt, most of the today, so when volcanoes formed in place they had the
atmosphere freezes out. time to become much more enormous than the rapidly
moving volcanoes on Earth. Overall, Mars appears to be
Modern Mars is a more dynamic planet today than we neither as dead as Mercury and our moon, nor as active
realized before the advent of frequent, high-resolution as Earth and Venus. As one scientist quips, “Mars is a
imaging. Hundreds of sets of before-and-after images warm corpse, if not a fire-breathing dragon.” Thanks to
from Mars Global Surveyor and Mars Reconnaissance the ongoing observations by current missions, however,
Orbiter document soil flowing down gullies, rocks this view of Mars is still evolving.
bouncing down hills, dunes migrating, craters forming,
icy layers receding and dust blowing. Cameras in orbit Mars almost resembles two different worlds that have
have even caught avalanches and tall whirlwinds as they been glued together. From latitudes around the equa-
happen. Image sequences from Spirit show the motions tor to the south are ancient highlands pockmarked with
of dust devils dancing across the landscape and clouds craters from the solar system’s early era, yet riddled with
scooting across the sky. Thus, the Martian landscape, channels that attest to the flow of water. The northern
which has changed dramatically in the past, continues third of the planet, however, overall is sunken and much
to change today. smoother at mile (kilometer) scales. Analysis of subsur-

Mars Science Laboratory Landing 57 Press Kit
face densities by their gravitational effect on orbiters • The Amazonian Era is the current age that began
supports a theory that an impactor almost big enough around 2 billion to 3 billion years ago. The planet is now
to be a planet itself bashed Mars early in Martian history, a dry, desiccating environment with only a modest atmo-
excavating the largest crater in the solar system. If that sphere in relation to Earth. In fact, the atmosphere is so
happened, it was long-enough ago that it would not ex- thin that pure water exposed to it can be stable only as
plain the smoothness of the northern plains. Theories for a solid or a gas, not as a liquid. The climate and perhaps
that range from proposing that the plains are the floor the stability of water at the surface may vary on scales of
of an ancient sea to proposing that the smoothness is thousands to millions of years as the tilt of the planet and
merely the end product of innumerable lava flows. its distance from the sun waver cyclically.

Scientists today view Mars as having had three broad Apart from that broad outline, there is lively debate and
ages, each named for a geographic area that typifies it: disagreement on the details of Mars’ history. How wet
was the planet, and how long ago? What eventually
• The Noachian Era is the name given to the time happened to all of the water? That is all a story that is
spanning roughly the first billion years of Mars’ existence still being written.
after the planet was formed 4.6 billion years ago. In this
era, scientists suspect that Mars was quite active with Even if we ultimately learn that Mars never harbored life
periods of warm and wet environments, erupting volca- as we know it here on Earth, scientific exploration of the
noes and some degree of tectonic activity. The planet Red Planet can assist in understanding the history and
may have had a thicker atmosphere to support flowing evolution of life on our own world. Much if not all of the
water, and it may have rained and snowed. evidence for the origin of life here on Earth has been
obliterated by the rapid pace of weathering and global
• In the Hesperian Era, which lasted for about the tectonics that have operated over billions of years. Mars,
next 500 million to 1.5 billion years, geologic activity was by comparison, is a composite world with some regions
slowing down and near-surface water perhaps was that may have histories similar to Earth’s ancient crust,
freezing to form surface and buried ice masses. Despite while others are a frozen gallery of the solar system’s
plunging temperatures, water pooled underground early days.
erupted when heated by impacts in catastrophic
floods that surged across vast stretches of the surface Thus, even if life never developed on Mars — something
— floods so powerful that they unleashed the force that we cannot answer just yet — scientific exploration
of thousands of Mississippi Rivers. Eventually, water of the planet may yield critical information unobtain-
became locked up as permafrost or subsurface ice, or able by any other means about the pre-biotic chemistry
was partially lost into outer space. that led to life on Earth. Mars as a fossil graveyard of
the chemical conditions that fostered life on Earth is an
intriguing possibility.

Mars Science Laboratory Landing 60 Press Kit
Program and Project Management
The Mars Science Laboratory Project is managed by Michael Meyer is lead scientist for the Mars Exploration
the Jet Propulsion Laboratory, Pasadena, Calif., for Program and program scientist for the Mars Science
NASA’s Science Mission Directorate, Washington. JPL Laboratory. Mary Voytek is deputy program scientist for
is a division of the California Institute of Technology in the Mars Science Laboratory. David Lavery is program
Pasadena. executive for the Mars Science Laboratory.

At NASA Headquarters, Washington, the Mars At JPL, Fuk Li is Mars Program manager and Roger
Exploration Program is managed by the Science Gibbs is deputy manager. Richard Zurek and David
Mission Directorate. John Grunsfeld is associate Beaty are Mars chief scientists. Peter Theisinger is Mars
administrator for the Science Mission Directorate and Science Laboratory project manager and Richard Cook
Charles Gay is deputy associate administrator. Douglas is deputy project manager. John Grotzinger, of Caltech, is
McCuistion is director of the Mars Exploration Program. Mars Science Laboratory project scientist, and Joy Crisp
and Ashwin Vasavada are deputy project scientists.